Microscale Chemistry Malaysian Adaptation

Microscale Chemistry Experiments: Adaptation to

Malaysian National Curriculum

School of Chemical Sciences

Universiti Sains Malaysia Penang, Malaysia

Prepared under UNESCO Contract No: 4500049693

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CONTENTS Foreword 6 Preface 8 List of apparatus 9 CHAPTER 1 INTRODUCTION TO CHEMISTRY SCIENTIFIC METHOD A. Investigating the effect of the temperature of water on the solubility of sugar 10 CHAPTER 2 THE STRUCTURE OF THE ATOM A. DIFFUSION OF PARTICLES IN SOLIDS, LIQUIDS AND GASES I. Diffusion of gases 12 II. Diffusion of liquids ** 13 III. Diffusion of solids 13 CHAPTER 3 CHEMICAL FORMULAE AND EQUATIONS A. DETERMINING THE EMPIRICAL FORMULA OF COPPER(II) 15 OXIDE ** B. CONSTRUCTING BALANCED CHEMICAL EQUATIONS I. Heating of copper(II) carbonate ** 18 II. Formation of ammonium chloride 19 III. Precipitation of lead(II) iodide 19 CHAPTER 4 PERIODIC TABLE OF ELEMENTS A. INVESTIGATING THE CHEMICAL PROPERTIES OF GROUP 17 ELEMENTS I. Reactions of halogens with water 21

a) Chlorine with water ** b) Bromine with water ** c) Iodine with water

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II. Reactions of halogen with iron 23

a) Chlorine with iron ** b) Bromine with iron ** c) Iodine with iron **

III. Reactions of halogens with sodium hydroxide, NaOH solution 25 a) Chlorine with sodium hydroxide, NaOH solution b) Bromine with sodium hydroxide, NaOH solution. c) Iodine with sodium hydroxide, NaOH solution

B. STUDYING THE PROPERTIES OF OXIDES OF THE ELEMENTS IN PERIOD 3 I. Reaction of oxides of Period 3 elements with water 29 II. Reaction of oxides of Period 3 elements with 2 M nitric acid and 30 2 M sodium hydroxide solutions CHAPTER 5 CHEMICAL BONDS A. PREPARATION OF IONIC COMPOUNDS I. Preparation of magnesium oxide 32 II. Preparation of iron(III) chloride ** 33 B. COMPARING THE PROPERTIES OF IONIC AND COVALENT COMPOUNDS I. Melting point and boiling point 35 II. Solubility in water and organic solvents 36 III.Electrical conductivity 37 CHAPTER 6 ELECTROCHEMISTRY A.CLASSIFYING CHEMICALS INTO ELECTROLYTES AND NON-ELECTROLYTES I. Molten substances 39 II. Aqueous solutions 40 B. ELECTROLYSIS OF MOLTEN COMPOUNDS 42 C. INVESTIGATING THE ELECTROLYSIS OF AQUEOUS SOLUTIONS I. Electrolysis of sodium hydroxide solution ** 44 II. Electrolysis of copper(II) sulphate solution 45 D. PURIFICATION OF COPPER 47

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E. ELECTROPLATING AN OBJECT WITH COPPER 49 F.PRODUCTION OF ELECTRICITY FROM CHEMICAL 51 REACTIONS IN A SIMPLE VOLTAIC CELL G.PRODUCTION OF ELECTRICITY FROM CHEMICAL REACTIONS 53 IN A DANIEL CELL H. CONSTRUCTING THE ELECTROCHEMICAL SERIES 55 USING THE PRINCIPLE OF DISPLACEMENT OF METALS CHAPTER 7 ACID AND BASES A. INVESTIGATING THE ROLE OF WATER IN SHOWING 57 THE PROPERTIES OF ACIDS B. STUDYING THE CHEMICAL PROPERTIES OF ACIDS I. Reactions of acids with bases 59 II. Reactions of acids with metals 61 III.Reactions of acids with metal carbonates 62 C. STUDYING THE CHEMICAL PROPERTIES OF BASES I. Reactions of bases with acids 64 II. Reactions of bases with ammonium salts 65 III.Reactions of bases with metal ions 65 D. MEASURING THE pH OF SOLUTIONS USED IN DAILY LIFE ** 67 E. DETERMINING THE END POINT OF THE TITRATION BETWEEN 69 HYDROCHLORIC ACID, HCl AND SODIUM HYDROXIDE, NaOH SOLUTION USING AN ACID-BASE INDICATOR ** CHAPTER 8 SALTS A. SOLUBILITY OF NITRATE, SULPHATE, CARBONATE AND 73 CHLORIDE SALTS B. PREPARATION OF SOLUBLE SALTS BY MIXING ACIDS WITH BASES I. To determine the volume of acid for neutralization 75 II. Preparation of the salt 76 III.Recrystallisation of the salt. 76

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C.PREPARATION OF SOLUBLE SALTS BY MIXING AN ACID 78 WITH AN INSOLUBLE METAL OXIDE D. PREPARATION OF INSOLUBLE SALTS BY CARRYING OUT A PRECIPITATION REACTION I. Preparation of lead(II) iodide 80 II. Preparation of lead(II) chromate(VI) 80 III.Preparation of barium sulphate 81 E.CONSTRUCTING THE IONIC EQUATION FOR THE 82 FORMATION OF LEAD(II) CHROMATE(VI) F. CARRYING OUT CHEMICAL TESTS TO IDENTIFY GASES I. Test for oxygen gas, O2 84 II. Test for hydrogen gas, H2 85 III. Test for carbon dioxide gas, CO2 86 IV. Test for ammonia gas, NH3 86 V. Test for chlorine gas 87 VI. Test for hydrogen chloride gas, HCl 87 VII.Test for sulphur dioxide gas, SO2 88 VIII.Test for nitrogen dioxide gas, NO2 89 G. STUDYING THE EFFECT OF HEAT ON CARBONATE AND NITRATE SALTS I. Carbonate salts ** 91 II. Nitrate salts 92 H. TESTING FOR THE PRESENCE OF ANIONS IN AQUEOUS SOLUTION I. Test for carbonate ion, CO32- 95 II. Test for chloride ion, Cl- 96 III.Test for sulphate ion, SO42- 96 IV.Test for nitrate ion, NO3- 97 CHAPTER 9 MANUFACTURED SUBSTANCES IN INDUSTRY A. PREPARATION OF AMMONIUM SULPHATE FERTILIZER I. To determine the volume of acid for neutralization 99 II. Preparation of the salt 100 ** Experiments from the UNESCO Advanced Teaching and Learning Packages on Microchemistry Experiences which have been adapted to the Malaysian National Curriculum (Form Four) website http://portal.unesco.org/science/en/ev.php-URL_ID=6816&URL_DO=DO_TOPIC&URL_SECTION=201.html

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FOREWORD

In Malaysia, Chemistry is offered to students at the upper secondary level beginning in Form Four (equivalent to Grade 10). The chemistry curriculum is organised based on the following themes: introduction to chemistry, matter around us, interactions between chemicals and production and management of manufactured chemicals. Central to the teaching-learning approach in the chemistry curriculum is practical work which involves scientific investigations and hands-on activities. It also has the potential to significantly enhance learning and development of conceptual understanding. Microscale chemistry is an approach to performing chemistry experiments which provides hands-on activities and personal experiences where students can do experiments individually. It is conducted by using reduced amounts of chemicals, miniature labware, safe, easy manipulative techniques and high quality skills. Using this approach, experiments in this manual have been developed at the School of Chemical Sciences, Universiti Sains Malaysia (USM) according to the chemistry syllabus for the Malaysian Form Four Integrated Curriculum for Secondary Schools (KBSM). I hope that with this manual of experiments, teachers will be encouraged to view microscale chemistry experiments as a viable alternative to conducting practical work in chemistry. In this respect, I would like to acknowledge the authors, Prof. Norita Mohamed, Mrs Mashita Abdullah and Assoc. Prof. Zurida Hj Ismail for their dedication in compiling this work. USM, through its innovative effort is proud to collaborate with any party, UNESCO in particular, in advancing further the use of microscale chemistry. Prof. Tan Sri Dato Dzulkifli Abdul Razak

VICE-CHANCELLOR UNIVERSITI SAINS MALAYSIA 11800 USM, PENANG MALAYSIA

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The Global Microscience Experiments Project, created by UNESCO in close cooperation with various international and national organisations, is very well known throughout the world. Many teaching and learning materials on Microscience experiments covering Primary Sciences, Chemistry, Biology and Physics have been prepared and are available free on the UNESCO website. However, the key point for the successful development of the project in a national level is the preparation of adapted versions of the existing materials to fit the national educational needs and curricula. Malaysian specialists have prepared the adapted version of the chemistry materials using part of UNESCOs learning materials with great success: 39 new experiments were tested using the advanced Microchemistry kits and 13 experiments were adapted from UNESCO materials. We hope that the present adapted version of the UNESCO learning materials in microchemistry and especially the 39 new experiments could be examined by other interested countries and could be used totally or partially in their own educational programs. We would like to congratulate warmly our Malaysian colleagues for the present publication and the excellent result which can constitute an example of best practice within the Global Microscience Experiments Project and a good model for use by other countries in the world. We believe that the Malaysian adaptation of Microchemistry Experiments contributes to a new phase of the Global Microscience Experiments Project whereby such adaptations become important components of the teaching and learning materials available to all. Maria Liouliou PROJECT COORDINATOR UNESCO, NATURAL SCIENCES SECTOR DIVISION OF BASIC AND ENGINEERING SCIENCES Academician Alexandre Pokrovsky DIRECTOR MICROSCIENCE EXPERIMENTS PROGRAM OF INTERNATIONAL ORGANISATION FOR CHEMICAL SCIENCES IN DEVELOPMENT (IOCD)

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PREFACE This manual of experiments has been prepared as a students learning package for Form Four (equivalent to Grade 10) secondary school students. The experiments have been designed using the Advanced Microchemistry Kit (Somerset Educational South Africa) and also glassware with a smaller volume. It comprises nine chapters which include: introduction to chemistry, the structure of the atom, chemical formulae and equations, periodic table of elements, chemical bonds, electrochemistry, acids and bases, salts and manufactured substances in industry. Thirteen experiments (marked with ** in the Table of Contents) in this manual have been adapted from experiments in the UNESCO Advanced Learning Package on Microchemistry Experiences prepared by the RADMASTE UNESCO Associated Centre of the University of Witwatersrand (South Africa) in cooperation with the Committee on Teaching of Chemistry of the International Union of Pure and Applied Chemistry (IUPAC) and UNESCO. The rest of the experiments (39) have been developed according to the Malaysian Form Four chemistry syllabus by replacing the traditional apparatus with microscale chemistry apparatus. Our continuing work with microscale chemistry experimentation with teachers and students through workshops held and school trials, have shown that with this approach, there is a reduction of up to 70 percent in chemical wastes produced and chemical costs, and a saving of up to 75 percent in time spent in conducting the experiments. We hope that with these experiments, teachers will be able to experience themselves the feasibility of conducting chemistry practical work with a microscale approach. We would like to especially acknowledge the assistance of Academician Alexandre Pokrovsky, Director of Microscience Experiments Programme IOCD and Prof. John D. Bradley, Director of RADMASTE Centre. We are also grateful to Prof. Wan Ahmad Kamil Mahmood, Dean of the School of Chemical Sciences for his support in the development of microchemistry experiments at Universiti Sains Malaysia. Prof. Norita Mohamed ([email protected]) Mrs Mashita Abdullah ([email protected]) SCHOOL OF CHEMICAL SCIENCES Assoc. Prof. Zurida Hj Ismail ([email protected]) SCHOOL OF EDUCATIONAL STUDIES UNIVERSITI SAINS MALAYSIA 11800 USM, PENANG MALAYSIA

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List of apparatus Advanced Microchemistry Kit (Somerset Educational) Big sample vial and lid Comboplate Combustion tube Crossarms for microstand Gas collecting tube Glass fusion tube Glass rod LED Lid 1 Lid 2 Microburner Microburette Microspatula Microstand Plasticine Propette Silicone tube Small sample vial and lid Straw electrodes Syringe Voltmeter Wire connections Other components 10 cm3 beaker 25 cm3 conical flask 10 cm3 measuring cylinder Blue litmus paper Battery 9V Durham tubes Filter funnel Microcrucible Microtripod stand Pencil lead Pipe-clay triangle Small wire gauze Test tube Thermometer Universal indicator paper W-tube Wire gauze

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Chapter 1: Introduction to Chemistry Scientific Method A. Investigating the effect of the temperature of water on the solubility of sugar Objective: To investigate the effect of the temperature of water on the solubility of

sugar Apparatus: 10 cm3 measuring cylinder, 10 cm3 beakers, electronic balance, microburner,

microtripod stand, wire gauze, glass rod, thermometer. Materials: Sugar and water.

Figure 1.1

Procedure:

1. Fill a measuring cylinder with 10 cm3 of water and pour it into a 10 cm3 beaker. 2. Record the temperature of the water with a thermometer. 3. Fill another 10 cm3 beaker with sugar. Weigh the beaker and its contents and

record the weight as a g. 4. Add the sugar a little at a time to the 10 cm3 of water in the beaker using a

microspatula. 5. Continue adding the sugar until no more sugar dissolves in the water. 6. Weigh the beaker with the sugar again and record the weight as b g. 7. The amount of sugar that dissolves in the water at room temperature is (b-a) g. 8. Repeat the experiment using water heated to different temperatures 40 C,

50 C, 60 C and 70 C each time. Heat the water using a microburner (refer to setting up of the microburner below).

9. Record the results in the following table.

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Setting up the microburner:

Fill three quarters of the microburner vial with methylated spirit. Attach the microburner lid (with glass tube and wick) to the vial and light the microburner.

Data and Observations:

Temperature (C) Room temperature 40 50 60 70

Initial mass of beaker and Its contents (g)

A b c d e

Final mass of beaker and its contents (g)

B c d e f

Mass of sugar dissolved (g) (b-a) (c-b) (d-c) (e-d) (f-e) Conclusions: Questions:

1. State the hypothesis for the experiment. 2. State:

(i) the manipulated variable. (ii) the responding variable. (iii) the fixed(controlled) variables of the experiment.

3. Plot a graph of the mass of sugar dissolved against temperature. (Both axes must be labeled with their units and the title of the graph must be given).

4. From the graph, give a conclusion for the experiment. References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. (2005). Chemistry practical book form 4, Integrated Curriculum for Secondary Schools, Abadi Ilmu Sdn. Bhd: Petaling Jaya. 2. Loh, W.L. & Tan, O.T. (2006). Exploring Chemistry Form 4. Fajar Bakti Sdn. Bhd: Shah Alam.

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Chapter 2: The Structure of the Atom A. Diffusion of particles in solids, liquids and gases Objective: To investigate the diffusion of particles in a gas, a liquid and a solid. Apparatus: Gas collecting tube, comboplate, small sample vial and lid, big sample vial

and lid, syringe, silicone tube, propette and plasticine. Materials: Liquid bromine, Br2, 1 mol dm-3 potassium manganate(VII), KMnO4 solution, potassium manganate(VII), KMnO4 crystals, hot liquid gel, tap water. Procedure:

I. Diffusion of gases

Figure 2.1

1. Put a gas collecting tube in well F1 of the comboplate in a vertical position using plasticine at the bottom of the well. 2. Take the comboplate into the fume chamber. 3. Use a clean, dry propette to add 2-3 drops of bromine into the tube. 4. Close the tube immediately and record any observations for several minutes. Watch Out! Liquid bromine, Br2 is toxic and corrosive. Wear gloves when handling this substance. This activity must be carried out in a fume chamber.

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II. Diffusion of liquids

Figure 2.2

1. Fill of a small sample vial with water. 2. Fill the syringe with 1 mol dm-3 of KMnO4 solution. 3. Attach the silicone tube to the nozzle of the syringe. 4. Carefully insert the silicone tube into the water in the vial until the open end

touches the bottom. 5. Press the plunger of the syringe slowly so that the KMnO4 solution flows down

the tube into the water at the bottom of the vial. 6. Carefully remove the tube and syringe. 7. Put a lid onto the vial and seal the hole in the lid with a piece of plasticine.

III. Diffusion of solids

Figure 2.3

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1. Fill a big sample vial with the hot gel solution and leave it aside to solidify. 2. Put some crystals of KMnO4 on the lid of the vial and close the vial containing the

gel. Put the vial upside down as shown in Figure 2.3. 3. Leave the vial for one day and record any changes which have occurred.


Experiments

Observations

I

II

III

Conclusions: Questions:

1. Why must the test tube in Section III be clamped upside down? 2. Based on your observations in Sections I, II and III, what can you conclude? 3. Based on your observations, arrange the rate of diffusion in a gas, a liquid and a

solid in ascending order. Explain your answer. 4. Based on your results, define diffusion. 5. In Section I, what will happen if you replace bromine, Br2 with a lighter gas such

as chlorine, Cl2? 6. What will you observe if you repeat the activity in Section II with boiling water?

References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L. L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn.Bhd: Petaling Jaya. 2. Bell, B. & Bradley, J.D. (2002). Advanced learning packages, Microchemistry experiences, Magister-Press Publishing House: Moscow.

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Chapter 3: Chemical Formulae and Equations A. Determining the empirical formula of copper(II) oxide Objective: To determine the empirical formula of copper(II) oxide Apparatus: Comboplate, 2 cm3 syringes, glass tube (6 cm x 4 mm), lid 1, lid 2,

microspatula, propette, 2 silicone tubes (4 cm x 4 mm), microburner and matches.

Materials: 2 mol dm-3 sulphuric acid, H2SO4, granulated zinc, Zn, 1 mol dm-3

copper(II) sulphate, CuSO4 solution, copper(II) oxide, CuO powder, and methylated spirit.

Figure 3.1 Procedure:

1. Use a microspatula to add about 0.5 to 1 g of granulated zinc to well F1. 2. Fill two thirds of well F6 with tap water from a propette. 3. Seal well F1 with lid 1. Seal well F6 with lid 2 so that the vent hole faces

outwards. 4. Connect one end of a silicone tube to the tube connector on lid 1. Connect one

end of the other silicone tube to the tube connector on lid 2. 5. Weigh the glass tube and record the weight. 6. Hold the glass tube in a horizontal position. Use the narrow end of a clean

microspatula to place a small quantity of copper(II) oxide powder in the center of the glass tube.

7. Weigh the glass tube with the copper(II) oxide and record its weight. 8. Keep the glass tube horizontal and attach one end to the silicone tube on lid 1.

Connect the other end to the silicone tube on lid 2. Note: keep the glass tube horizontal at all times otherwise the powder might spill into well F1 or F6.

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9. Fill the syringe with 1 ml of 2 mol dm-3 sulphuric acid. Fit the nozzle of the syringe into the syringe inlet on lid 1.

Watch Out! Be careful when you handle acids. Acids are corrosive.

10. Light the microburner (refer to pg 11, Chap 1) and place it away from the

comboplate. 11. Add the sulphuric acid very slowly from the syringe into well F1. 12. Using a propette, add slowly through the tube connector, 2 3 drops of

copper(II) sulphate solution into well F1. 13. When a few bubbles have come through the water in well F6, bring the flame of

the microburner to the middle of the glass tube where the copper(II) oxide powder has been placed. Hold the microburner in this position.

Caution: Do not bring the flame of the microburner near the silicone tubes

(as they will melt) or the vent of well F1 (as hydrogen is explosive)

14. Stop heating the copper(II) oxide powder after about 2 minutes or after it has changed in appearance. Blow out the microburner flame.

15. Continue the flow of hydrogen gas, H2, until the apparatus cools down to room temperature.

16. Weigh the glass tube and its content and record the weight. 17. If there is water being sucked up from well F6 into the glass tube, disconnect

lid 2 from well F6. 18. Repeat heating, cooling and weighing in steps 13 to 16 until a constant mass is

achieved. Record the constant mass in your notebook.

Caution: A mixture of hydrogen and air will explode when lighted. Note: The 2 mol dm-3 sulphuric acid, granulated zinc and 1 mol dm-3 copper(II)

sulphate solution can be replaced by 5.5 mol dm-3 hydrochloric acid and zinc powder.


Description Mass (g) Glass tube Glass tube + copper(II) oxide Glass tube + copper Copper Oxygen Moles Moles of copper Moles of oxygen Mole ratio

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1. Describe what happens to the CuO(s). 2. What other changes occur in the glass tube? 3. What chemical reaction has occurred in the tube? Write down the chemical

reaction for the production of hydrogen. 4. Why do you need to repeat heating, cooling and weighing until a constant mass is

achieved? 5. Based on your results, calculate the empirical formula of copper(II) oxide.

References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya. 2. Bell, B. & Bradley, J.D. (2002). Advanced learning packages, Microchemistry experiences, Magister-Press Publishing House: Moscow.

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Chapter 3: Chemical Formulae and Equations B. Constructing balanced chemical equations Objective: To construct balanced chemical equations Apparatus: Comboplate, glass fusion tube, silicone tube, crossarms for microstand,

microspatula, propettes, lid 2, microburner, W-tube. Materials: Copper(II) carbonate, CuCO3 powder, lime water, Ca(OH)2, concentrated

hydrochloric acid, HCl, concentrated ammonia, NH3 solution, lead(II) nitrate, Pb(NO3)2 solution and potassium iodide, KI solution.

Procedure: I. Heating of copper(II) carbonate

Figure 3.2

1. Hold the fusion tube in a horizontal position. Use the narrow end of a plastic microspatula to fill about of the fusion tube with copper(II) carbonate powder. Note its color.

2. Set up the apparatus as shown in Figure 3.2 (refer to pg 11, Chap 1 for setting up of microburner).

3. Heat the copper(II) carbonate and pass the gas produced through limewater in well F4. Observe what happens to the copper(II) carbonate and the limewater.

4. When the reaction is completed, withdraw the silicone tube. 5. Record the observations in the notebook.

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II. Formation of ammonium chloride

Figure 3.3

1. Using a propette, place three or four drops of concentrated hydrochloric acid in one of the outer tubes of the W-tube.

2. Using another propette, place three or four drops of concentrated ammonia solution into the other outer tube of the W-tube.

3. Shake the W-tube carefully to allow the gases to flow. Caution: Do not shake vigorously. It may cause the solutions to mix together.

4. Observe what happens in the middle of the W-tube and record your observations. Caution: Concentrated hydrochloric acid and ammonia are corrosive and

harmful. Therefore, handle these solutions carefully and carry out these activities in the fume chamber.

III. Precipitation of lead(II) iodide

Figure 3.4

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1. Using a propette, place the lead(II) nitrate solution until of well F1 of the comboplate is filled up.

2. Add the potassium iodide solution until half of the well is filled up. 3. Stir the mixture using a microspatula and observe what happens. 4. Record your observations in your notebook.

Data and Observations: Section Reactants Products

I

II

III


1. Construct a table to fill in the following data. a) The reactants and products in Sections I, II and III. b) The state of each reactant and product that is whether it exists as a solid,

liquid, gas or aqueous solution. c) The chemical formula of each of the reactants and products.

2. Write a balanced chemical equation for each reaction that occurs.

References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya. 2. Bell, B. & Bradley, J.D. (2002). Advanced learning packages, Microchemistry experiences, Magister-Press Publishing House: Moscow. 3. Gupta, H.O. (2007). A novel W-Tube for microscale experiments in chemistry. Journal of Chemical Education, 84(2), 321.

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Chapter 4: Periodic table of elements A. Investigating the chemical properties of group 17 elements. Objective: To investigate the chemical properties of group 17 elements. I. Reactions of halogens with water Apparatus: Comboplate, syringe, silicone tube, lid 1, lid 2, propette, microspatula,

blue litmus paper. Materials: 2 mol dm-3 hydrochloric acid, HCl, household bleach, potassium bromide,

KBr solution, potassium manganate(VII), KMnO4, iodine, I2 solid, distilled water.

Caution: Chlorine gas, bromine gas and solid iodine are poisonous. Carry out the

experiment in the fume chamber. Wear gloves and safety goggles when handling these halogens.

Procedure: a) Chlorine with water

Figure 4.1

1. Pass the chlorine gas into 1 cm3 of distilled water in well F2, as shown in Figure 4.1.

2. Put a piece of blue litmus paper into the solution produced in well F2. 3. Observe any changes in colour. 4. Record the observations in a table in your notebook.

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b) Bromine with water

Figure 4.2

1. Pass the bromine gas into 1 cm3 of distilled water in well F3, as shown in Figure 4.2.

2. Put a piece of blue litmus paper into the solution produced. 3. Observe any changes in colour. 4. Record the observations in your notebook.

c) Iodine with water

Figure 4.3

1. Put a small piece of solid iodine into 1 cm3 of distilled water in well F4. 2. Stir the mixture using a microspatula until no further changes occur. 3. Put a piece of blue litmus paper into the solution produced. 4. Observe any changes in colour. 5. Record the observations in a table.

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II. Reactions of halogens with iron Apparatus: Comboplate, syringe, silicone tube, glass tube, propette, fusion tube,

crossarms microstand, microburner, plasticine. Materials: 2 mol dm-3 hydrochloric acid, HCl, household bleach, iron, Fe powder,

potassium bromide, KBr, potassium manganate(VII), KMnO4, solid iodine, I2, hot water, soda lime.

Procedure: a) Chlorine with iron

Figure 4.4

1. Set up the apparatus as shown in Figure 4.4. 2. Heat the iron powder in the glass tube strongly with a microburner (refer to pg 11,

Chap 1 for setting up of microburner). 3. When the iron powder becomes red hot, add the 1.0 cm3 of hydrochloric acid very

slowly using the syringe, so that the chlorine gas produced will pass over the hot iron powder.

4. Observe any changes. Record the observations in a table in your notebook.

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b) Bromine with iron

Figure 4.5

1. Set up the apparatus as shown in Figure 4.5. 2. Heat the iron powder in the combustion tube strongly. 3. When the iron powder becomes red hot, add the potassium manganate(VII)

solution very slowly, so that the bromine gas produced will pass over the hot iron powder.

4. Observe any changes. Record your observations in a table in your notebook. c) Iodine with iron

Figure 4.6

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1. Put some iodine in a fusion tube and set up the apparatus as shown in Figure 4.6. 2. Heat the iron powder in the glass tube strongly. 3. When the iron powder becomes red hot, heat the iodine crystals in the fusion tube

to sublime it. 4. Pass the iodine vapor over the hot iron powder until no further changes occur. 5. Record your observations in a table in your notebook.

III. Reactions of halogens with sodium hydroxide, NaOH solution Apparatus: Comboplate, syringe, silicone tube, lid 1, lid 2, propette, microspatula. Materials: 2 mol dm-3 hydrochloric acid, HCl, household bleach, potassium bromide,

KBr, potassium manganate(VII), KMnO4, iodine, I2 solid, 2 mol dm-3 sodium hydroxide, NaOH solution.

Procedure: a) Chlorine with sodium hydroxide, NaOH solution

Figure 4.7

1. Pass the chlorine gas into 1 cm3 of sodium hydroxide solution in well F2, as shown in Figure 4.7.

2. Observe any changes in colour. Record your observations in your notebook. Caution: Be careful when handling halogens and sodium hydroxide solution.

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b) Bromine with sodium hydroxide, NaOH solution.

Figure 4.8

1. Pass the bromine gas into 1 cm3 of sodium hydroxide solution in well F3 as shown in Figure 4.8.

2. Observe any changes in colour. Record your observations in your notebook. c) Iodine with sodium hydroxide, NaOH solution

Figure 4.9

1. Put a small piece of solid iodine, I2 into 1 cm3 of sodium hydroxide solution in well F4.

2. Stir the mixture using a microspatula until no further changes occur.

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3. Observe any changes in colour. 4. Record your observations in a table in your notebook.


Observation Halogen

Reactant Chlorine Bromine Iodine

Water

Iron powder

Sodium hydroxide

Construct a hypothesis for the experiment involving halogens and sodium hydroxide. State the variables and the operational definition. Conclusions: Questions:

1. In Section I, a) State the properties exhibited by each halogen when they react with water. b) What are the products formed when chlorine, bromine and iodine react

with water? c) Write the chemical equations for the reactions.

2. What is the function of soda lime in Section II?

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3. Why must the iron powder be heated first before these halogens are passed over it in Section II?

4. a) What are the products for the reactions between chlorine, bromine and iodine with iron?

b) Write the chemical equations for these reactions. 5. a) What are the products when chlorine, bromine and iodine react with sodium

hydroxide, NaOH solution? b) Write the chemical equations for these reactions.

6. Describe the changes in reactivity of Group 17 elements when going down the group. Explain your answers.

References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya. 2. Bell, B. & Bradley, J.D. (2002). Advanced learning packages, Microchemistry experiences, Magister-Press Publishing House: Moscow. 3. Microscale gas chemistry: experiments with chlorine. Retrieved from: http://mattson.creighton.edu/Microscale_Gas_Chemistry.html.

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Chapter 4: Periodic table of elements B. Studying the properties of oxides of the elements in Period 3. Objective: To study the properties of the oxides of elements in Period 3. Apparatus: Comboplate, microspatulas, propette, syringe, glass rod, microburner, and

2 cm3 syringe. Chemicals: Sodium oxide, Na2O, magnesium oxide, MgO, aluminium oxide, Al2O3,

silicone(IV) oxide, SiO2, phosphorus pentoxide, P2O5, universal indicator solution, 2 mol dm-3 nitric acid, HNO3, and 2 mol dm-3 sodium hydroxide, NaOH solution distilled water.

Procedure: I. Reaction of oxides of Period 3 elements with water.

Figure 4.10

1. Use a clean propette to fill half of wells F1 to F5 with distilled water. 2. Use the spooned ends of different microspatulas to add sodium oxide, magnesium

oxide, aluminium oxide, silicone dioxide, and phosphorus pentoxide to wells F1 to F5 respectively.

3. Stir the solution using the microspatula and observe the solubility of the oxides. 4. Add one drop of universal indicator solution to each solution and record the pH of

the solution.

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II. Reaction of oxides of Period 3 elements with 2 M nitric acid and 2 M sodium hydroxide solutions

Figure 4.11

1. Use the spooned end of a microspatula to place one level spatula of sodium oxide

powder into wells F1 and E1 of the comboplate. 2. Fill the syringe with 0.5 cm3 of nitric acid and 0.5 cm3 of sodium hydroxide to the

contents in each well F1 and E1. 3. Light the microburner (refer to pg 11, Chap 1) and fully heat one end of the glass

rod in the flame. Caution: Do not keep the rod in the flame for a long period.

4. Heat the reaction mixture in F1 by stirring with the heated glass rod. 5. Rinse and dry the rod, and repeat the heating process a few times. 6. Repeat this process to the contents of E1. 7. Record the solubility of sodium oxide in the two solutions. 8. Repeat the experiment with magnesium oxide, aluminium oxide, silicon(IV)

oxide and phosphorus(V) oxide respectively in wells F2 to F5 and E2 to E5. Data and Observations:

Observations I. Oxide Solubility in water pH values of solution

Inference

Na2O

MgO

Al2O3

SiO2

P2O5

31

II. Oxide Solubility in 2 mol dm-3

NaOH Solubility in 2 mol dm-3

HNO3 Inference

Na2O

MgO

Al2O3

SiO2

P2O5


1. Why are nitric acid and sodium hydroxide solution used in this experiment? 2. Write the chemical equations for all the reactions of the oxides of Period 3

elements with water, if any. 3. Write the chemical equations for the reactions of sodium hydroxide solution and

nitric acid with a) Magnesium oxide, MgO, if any. b) Aluminium oxide, Al2O3, if any.

References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya.

32

Chapter 5: Chemical bonds A. Preparation of ionic compounds Objective: To prepare ionic compounds I. Preparation of magnesium oxide Apparatus: Microcrucible, microtripod stand, pipe-clay triangle, microburner. Materials: Magnesium ribbon, sand paper and methylated spirit. Procedure:

Figure 5.1

1. Obtain a 2 cm length of magnesium ribbon. 2. Use sand paper to remove the oxide layer on the surface of the magnesium ribbon. 3. Place the magnesium ribbon in a microcrucible as shown in Figure 5.1. 4. Heat the magnesium ribbon strongly with a microburner (refer to pg 11, Chap 1). 5. Observe what happens to the magnesium ribbon. Record it in your notebook.

33

II. Preparation of iron(III) chloride Apparatus: Comboplate, syringe, silicone tube, glass tube, propette and microburner. Materials: Iron, Fe powder, household bleach, 2 mol dm-3 Hydrochloric acid, HCl

and sodium hydroxide, NaOH solution.


1. Setup the apparatus as shown in Figure 5.2. 2. Heat the iron powder in the glass tube strongly. 3. When the iron powder becomes red hot, add the 1.0 cm3 of hydrochloric acid

using the syringe very slowly, so that the chlorine gas produced passes over the hot iron powder.

4. Observe any changes. Record your observations in a table in your notebook.

Watch Out! Chlorine gas is poisonous. Do not inhale the gas. Data and Observations: Experiment Observations

I

II

34


1. a) What are the products of all three reactions? b) Give the chemical equations for the reactions.

References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya. 2. Bell, B. & Bradley, J.D. (2002). Advanced learning packages, Microchemistry experiences, Magister-Press Publishing House: Moscow. 3. Microscale gas chemistry: experiments with chlorine. Retrieved from: http://mattson.creighton.edu/Microscale_Gas_Chemistry.html.

35

Chapter 5: Chemical bonds B. Comparing the properties of ionic and covalent compounds Objective: To compare the properties of ionic and covalent compounds I. Melting point and boiling point Apparatus: Comboplate, microspatula, propette. Materials: Sodium chloride, NaCl, sodium sulphate, Na2SO4, diethyl ether, (C2H5)2O

and hexane, C6H14. Procedure:

Figure 5.3

1. Use the spooned end of a microspatula to place one level spatula of sodium chloride and sodium sulphate into wells F1 and F2 of the comboplate.

2. Use the propette to place three drops of diethyl ether and hexane into wells F3 and F4 respectively.

3. Observe their physical states. Leave them aside for 5 minutes and then observe what happens.

4. Make inferences regarding their melting points and boiling points.

36


Compound Physical state After 5 minutes Inference

Sodium chloride

Sodium sulphate

Diethyl ether

Hexane

II. Solubility in water and organic solvents Apparatus: Comboplate, Durham tubes, propette. Materials: Sodium chloride, NaCl, sodium sulphate, Na2SO4, diethyl ether, (C2H5)2O,

hexane, C6H14 and cyclohexane, C6H12.


1. Use a spooned end of a microspatula to place two leveled spatulas of sodium chloride in a Durham tube. Add 10 drops of water into it. Shake and observe whether sodium chloride is soluble or not in water.

2. Place the Durham tube slanting in well F1 of the comboplate. 3. Repeat steps 1 and 2 using cyclohexane as a solvent in place of water. 4. Repeat steps 1 to 3 by using two leveled spatulas of sodium sulphate. 5. Repeat steps 1 to 3 by using 10 drops of diethyl ether. 6. Repeat steps 1 to 3 by using 10 drops of hexane.

37


Solubility Compound In water In organic solvent

Sodium chloride

Sodium sulphate

Diethyl ether

Hexane

III. Electrical conductivity Apparatus: Microcrucible, battery 9V, LED, pencil lead, carbon electrodes,

comboplate, microburner, microspatula, wire gauze and microtripod stand. Materials: Solid lead(II) bromide, PbBr2, glucose, C6H12O6, 1 mol dm-3 sodium

chloride solution, NaCl.

Figure 5.5 Figure 5.6 Procedure:

1. Fill a microcrucible with solid lead(II) bromide until it is half full. 2. Set up the apparatus as shown in Figure 5.5 (refer to pg 11, Chap 1 for setting up

of microburner). 3. Observe whether the LED lights up or not. 4. Heat the solid lead(II) bromide until it melts. 5. Observe again whether the bulb lights up or not.

38

6. Repeat steps 1 to 5 using glucose instead of lead(II) bromide. 7. Use the set-up of apparatus in Figure 5.6 to test the electrical conductivity of the

sodium chloride solution. Data and observations:

Compound State Observation Inference

Solid Lead(II) bromide Molten

Solid Glucose Molten

Solid

Sodium chloride Aqueous solution


1. What can you generalize about the melting point, boiling point, solubility and electrical conductivity for both covalent and ionic compounds?


39

Chapter 6: Electrochemistry A. Classifying chemicals into electrolytes and non-electrolytes Objective: To classify substances into electrolytes and non-electrolytes Apparatus: 9V battery, pencil leads, LED, microcrucible, microburner, microtripod

stand, small wire gauze, comboplate, propette. Materials: Lead(II) bromide, PbBr2, naphthalene, C10H8, 0.1 mol dm-3 sodium

hydroxide, NaOH solution, 0.1 mol dm-3 glucose solution and 0.1 mol dm-3 copper(II) sulphate, CuSO4 solution.

Procedure: Caution: Carry out Part I of the experiment in the fume chamber. I. Molten substances

Figure 6.1

1. Fill a microcrucible with solid lead(II) bromide until it is half full. 2. Set up the apparatus as shown in Figure 6.1. 3. Using a microburner (refer to pg 11, Chap 1), heat the solid lead(II) bromide until

it has melted completely. 4. Connect the battery clip of the LED to the terminals of the 9V battery and pencil

leads. 5. Immerse both the pencil leads into the molten lead(II) bromide. 6. Record your observations in your notebook. 7. Repeat steps 1 to 6, replacing the solid lead(II) bromide with naphthalene.

40

II. Aqueous solutions

Figure 6.2

1. Use the propette to add sodium hydroxide solution into well E1. Rinse the propette with tap water to clean it.

2. Push the lid with the current indicator into well E6. 3. Connect the battery clip of the current indicator into well E6. 4. Connect each of the crocodile clip to the carbon rod (pencil leads) as shown in

Figure 6.2. 5. Insert the carbon rod connected to the long black wire into solution in well E1.

Insert the carbon rod connected to the long end of the red wire into the same solution in well E1. Make sure that the carbon rods do not touch in the solution.

6. Observe what happens to the red light emitting diode (LED) in the current indicator. Wipe the carbon rods clean.

7. Repeat steps 1-6 using the copper(II) sulphate solution and glucose solution. Use wells E2, F1 and F2.

Data and Observation:

Substance LED glow Does reaction occur Electrolyte or non-electrolyte

Molten lead (II) bromide

Molten naphthalene

Sodium hydroxide solution

Glucose solution

Copper(II) sulphate solution

41


1. What substances conduct electricity? 2. What substances do not conduct electricity? 3. What type of substances are electrolytes? 4. What type of substances are non-electrolytes?


42

Chapter 6: Electrochemistry B. Electrolysis of Molten compounds Objective: To investigate the electrolysis of molten lead(II) bromide, PbBr2. Apparatus: 9V battery, pencil leads, current indicator (LED) with wire connection,

microcrucible, microburner, microtripod stand and small wire gauze. Materials: Lead(II) bromide, PbBr2. Procedure:

Figure 6.3

1. Fill a microcrucible with lead(II) bromide until it is half full. 2. Place the microcrucible on the wire gauze. 3. Set up the apparatus as shown in Figure 6.3. 4. Using the microburner (refer to pg 11, Chap 1), heat the solid lead(II) bromide

until it melts. 5. Connect the battery clip of the current indicator to the terminals of the 9 V

battery. 6. Connect each of the crocodile clip to the pencil leads as shown in Figure 6.3. 7. Immerse both of the pencil leads into the molten lead(II) bromide. 8. Observe what happens at the anode. Record all your observations in your

notebook. 9. After 4 minutes, remove the crocodile clips from the pencil leads. 10. Carefully pour out the molten lead(II) bromide into a small beaker to observe

what is formed at the cathode. 11. Record your observations in your notebook.

43


Electrode Observation

Inference

Anode

Cathode


1. Name the ions that move to the cathode and the anode during electrolysis. 2. Write half equations that represent the reactions that occur at the

a) Anode b) Cathode

3. Write the overall equation that represents the electrolysis of lead(II) bromide, PbBr2.


44

Chapter 6: Electrochemistry C. Investigating the electrolysis of aqueous solutions Objective: To investigate the electrolysis of aqueous copper(II) sulphate, CuSO4 solution and sodium hydroxide, NaOH solution. Apparatus: Comboplate, 9V battery, current indicator (LED) with wire connections, 2

straw electrodes, 1 straw electrode (with carbon electrode), 1 x carbon electrode (pencil lead), sample vial, box of matches, thin stemmed propette.

Materials: 1.0 mol dm-3 sodium hydroxide, NaOH and 1.0 mol dm-3 copper(II) sulphate, CuSO4 solution.

Figure 6.4 Procedure: I. Electrolysis of sodium hydroxide solution

1. Push the current indicator into well E6 of the comboplate. 2. Mark each of the drinking straw electrodes using a permanent marker pen. Let

one of the electrodes be called electrode 1 and the other electrode 2. 3. Fill half of the sample vial with 1.0 mol dm-3 sodium hydroxide solution. Place

the vial into well E5 next to the current indicator in well E6. 4. Hold electrode 1 with the open end upwards and fill the electrode completely with

1.0 mol dm-3 sodium hydroxide solution from the propette.

45

5. Quickly turn electrode 1 the other way up and place it into the solution in the small sample vial. Repeat this procedure for electrode 2. Return any remaining solution in the propette to the small sample vial. Use tap water to thoroughly rinse your fingers free of the sodium hydroxide solution.

6. Connect the end of the black wire from the current indicator to the negative (-) terminal of the battery. Connect the end of the short black wire to electrode 1.

7. Connect the end of the red wire to the positive terminal (+) of the battery. Connect the other end of the red wire to electrode 2.

8. Let the substance produced in electrode 1 be called substance A. Let the substance produced in electrode 2 be called substance B.

9. Record any observation at the anode, cathode and in the electrolytes. 10. Test the gas gathered at the cathode by using a lighted splinter. 11. Test the gas gathered at the anode by using a glowing splinter. 12. Record all the results.

II. Electrolysis of copper(II) sulphate solution

1. Push the current indicator into well E6 of the comboplate. 2. Fill half of the sample vial with 1.0 mol dm-3 copper(II) sulphate solution. Place

the vial into well E5 next to the current indicator in well E6. 3. Hold the straw electrode (with carbon electrode) with the open end upwards and

fill the electrode completely with 1.0 mol dm-3 copper(II) sulphate solution from the propette.

4. Quickly turn the electrode the other way up and place it into the solution in the small sample vial. Return any remaining solution in the propette to the small sample vial. Use tap water to thoroughly rinse your finger free of the copper(II) sulphate solution.

5. Place the carbon electrode (pencil lead) into the solution in the sample vial. 6. Connect the end black wire from the current indicator to the negative (-) terminal

of the battery. Connect the end of the short black wire to the carbon electrode. 7. Connect the end of the red wire to the positive terminal (+) of the battery. Connect

the other end of the red wire to straw electrode. 8. Record any observation at the anode, cathode and in the electrolytes. 9. Light the match. Carefully remove straw electrode from the solution, sealing the

open end with your finger when it is out of the solution. Bring the electrode very close to the glowing splinter.

Data and Observations: Electrolyte Observations Cathode Anode Change in solution Sodium hydroxide

Copper(II) sulphate

46


1. For the electrolysis of copper(II) sulphate solution, a) Identify the cations and anions. b) What are the ions that move to the anode and to the cathode? c) Which ions have been discharged at the anode and at the cathode? d) Write half equations representing the reactions that occur at the anode and

the cathode. 2. Draw a diagram which shows what happens during the electrolysis of dilute

sulphuric acid, H2SO4. The diagram should show:

a) The ions present in dilute sulphuric acid, H2SO4. b) The movement of ions to the anode and the cathode. c) The discharge of ions at the anode and the cathode and their respective half

equations. References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya. 2. Bell, B. & Bradley, J.D. (2002). Advanced learning packages, Microchemistry experiences, Magister-Press Publishing House: Moscow.

47

Chapter 6: Electrochemistry D. Purification of copper Objective: To investigate the purification of copper Apparatus: 9V heavy duty battery, comboplate, current indicator (LED) with wire connections, sample vial and thin stemmed propette. Materials: 1 mol dm-3 copper(II) sulphate, CuSO4 solution, impure copper plate, pure

copper plate.


1. Push the current indicator into well E6 of the comboplate. 2. Remove the lid from the small sample vial and fill half of the vial with 1.0 mol

dm-3 copper(II) sulphate solution. Place the vial into well E5 next to the current indicator in well E6.

3. The apparatus as shown in the figure 6.5 is set up using the impure copper plate as the anode and the pure copper plate as the cathode.

4. Allow the electric current to pass through the electrolyte for 5 10 minutes. 5. Record any changes at the anode and the cathode. 6. Repeat steps 1 to 5 using impure copper as the cathode and pure copper as the

anode.

48


Electrode Observation

Anode Cathode Anode Cathode

Impure copper Pure copper

Pure copper Impure copper

Conclusions: References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya.

49

Chapter 6: Electrochemistry E. Electroplating an object with copper Objective: To investigate the electroplating of an object with copper Apparatus: 9V heavy duty battery, comboplate, current indicator (LED) with wire connections, sample vial and thin stemmed propette. Materials: 1.0 mol dm-3 copper(II) sulphate solution, copper electrode/plate, iron nail, sandpaper.


1. Clean a piece of iron nail with sand paper. Wash the iron nail with detergent and rinse thoroughly with water.

2. Push the current indicator into well E6 of the comboplate. 3. Remove the lid from a small sample vial and fill half of the vial with 1.0 mol dm-3

copper(II) sulphate solution. Place the vial into well E5 next to the current indicator in well E6.

4. Set up the apparatus using the iron nail as the cathode and a copper electrode as the anode as shown in figure 6.6.

5. Switch the current off after 2 3 minutes. 6. Remove the iron nail from the electrolyte and dry it. Record the change to the iron

nail. 7. Repeat steps 1 6 by using copper as the cathode and iron nail as the anode.

50


Electrode Set Anode Cathode

Observation

I Copper Iron nail

II Iron nail Copper


1. What three conditions are necessary to electroplate an iron spoon with copper? 2. A good electroplating process is one that results in an even thin layer of coating.

Suggest 2 ways on how this can be achieved.


51

Chapter 6: Electrochemistry F. Production of electricity from chemical reactions in a simple voltaic cell

Objective: To show the production of electricity from chemical reactions in a simple voltaic cell Apparatus: 1 x Comboplate, 1 x thin stemmed propette, wire connections, 1 x voltmeter, 1 x sample vial. Materials: 1.0 mol dm-3 Sodium chloride, NaCl solution, copper plate and magnesium

ribbon.


1. Clean a piece of magnesium ribbon and a copper plate with sandpaper. 2. Fill half of the small sample vial with 1.0 mol dm-3 sodium chloride solution.

Place the vial into well E6. 3. Immerse the magnesium ribbon and copper plate in the sodium chloride solution

and connect both metals to the voltmeter/multimeter by using the wire connections.

4. Record the reading of the voltmeter and any changes at the electrodes. 5. Repeat steps 1 to 4 using the copper plate instead of magnesium ribbon.

52


Type of metal Voltmeter reading (V) Observation

Magnesium/copper (Mg/Cu)

Copper/copper (Cu/Cu)


1. Explain how electricity is produced in a simple voltaic cell. Give the half equations for the reactions that take place.

2. Predict what will happen if sodium chloride, NaCl solution is replaced by potassium sulphate, K2SO4 solution. Give your reasons.


53

Chapter 6: Electrochemistry G. Production of electricity from chemical reactions in a Daniel cell Objective: To show the production of electricity from chemical reactions in a Daniel cell Apparatus: 1 x comboplate, 2 x thin stemmed propette, 2 wire connections, 1 x multimeter/voltmeter, filter paper, scissors. Materials: 1.0 mol dm-3 copper(II) nitrate, Co(NO3)2 solution, 1.0 mol dm-3 zinc nitrate

Zn(NO3)2 solution, copper strip, zinc foil, potassium nitrate, KNO3, saturated solution.


1. Using the E row of the comboplate, fill half of E1 and E2 with copper(II) nitrate and zinc nitrate solution respectively.

2. Make a salt bridge from the filter paper. Cut the paper into a shape given below so that it will form a continuous bridge between 2 wells.

54

3. To make the salt bridge complete, place the cut out filter paper into a beaker containing a saturated solution of potassium nitrate. Remove the salt bridge and place it into wells E1 and E2.

4. Clean up the copper plate and zinc foil with sand paper. 5. Immerse the copper plate in the copper(II) nitrate solution and zinc foil in the zinc

nitrate solution. Connect both metals to the voltmeter/multimeter using the wire connections.

6. Observe what happens to the voltmeter, zinc foil, copper plate and copper(II) nitrate solution.


Type of metal Observation

Zinc

Copper

Copper(II) sulphate solution

Voltmeter

Conclusions: References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya. 2. Tan, Y.T., Loh, W.L. & Tan, O.T. (2007). Success Chemistry SPM, Integrated Curriculum for Secondary School, Oxford Fajar Sdn. Bhd: Shah Alam. 3. Microscale 30 Voltaic cells. http://dwb.unl.edu/Chemistry/MicroScale/MScale20.html

55

Chapter 6: Electrochemistry H. Constructing the electrochemical series using the principle of displacement of metals Objective: To construct the electrochemical series using the principle of displacement of metals Apparatus: Comboplate, thin stemmed propette Materials: 1.0 mol dm-3 copper(II) nitrate, Cu(NO3)2 solution, 1.0 mol dm-3 lead(II)

nitrate, Pb(NO3)2 solution, 1.0 mol dm-3 zinc nitrate, Zn (NO3)2 solution, 1.0 mol dm-3 magnesium nitrate, Mg(NO3)2 solution, copper strip, lead strip, zinc strip, magnesium ribbon and sand paper.


1. Fill half of F1, F2, F3 and F4 wells in the comboplate with copper(II) nitrate solution.

2. Clean a piece of copper strip, lead strip, zinc strip and magnesium ribbon respectively with sand paper and drop into each of the wells.

3. Allow the reaction to proceed for five minutes. 4. Observe any changes in the colour of the solution and whether any metals are

deposited. 5. Repeat step 1 to 4 by using lead(II) nitrate solution, zinc nitrate solution and

magnesium nitrate solution respectively to replace copper(II) nitrate solution. 6. Record the results of the experiment in a table below.

56

Data and Observations: Solution Metals

Copper(II) nitrate Lead(II) nitrate Zinc nitrate Magnesium nitrate

Copper

Lead

Zinc

Magnesium


1. Why is magnesium not displaced by any other metals in this experiment? 2. Write the equations to show all displacement reactions involving zinc.

References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya. 2. Eng, N.H., Lim, E.W. & Lim, Y.C (2006).Focus excel chemistry form 4. Penerbitan Pelangi Sdn. Bhd: Bangi.

57

Chapter 7: Acids and Bases A. Investigating the role of water in showing the properties of acids Objective: To investigate the role of water in showing the properties of acids Apparatus: Comboplate, thin stemmed propettes, microspatula Materials: Glacial ethanoic acid, CH3COOH, ethanol, C2H5OH, blue litmus paper, water. 1 2 3 4 5 6 F E D C


1. Place a piece of dry blue litmus paper in well F1 of the comboplate. 2. Use the propette to draw up some dry glacial ethanoic acid. 3. Place a few drops of the glacial ethanoic acid onto the blue litmus paper. 4. Observe the effect of the glacial ethanoic acid on the litmus paper. Record your

observations in the table. 5. Repeat steps 1 to 4 using ethanoic acid in water and ethanoic acid in ethanol to

replace glacial ethanoic acid in the wells F2 and F3. 6. Tabulate the observations in the table.

Blue litmus paper+ ethanoic acid

Blue litmus paper+ ethanoic acid+water

Blue litmus paper+ ethanoic acid+ ethanol

58


Type of acid

Observation

Glacial ethanoic acid, CH3COOH

Ethanoic acid, CH3COOH in water

Ethanoic acid, CH3COOH in ethanol


1. What is the ion responsible for changing the colour of blue litmus paper? How is it produced?

2. Why does glacial ethanoic acid, CH3COOH not show acidic properties? 3. When ethanoic acid, CH3COOH is dissolved in propanone, CH3COCH3, it does

not change the colour of blue litmus paper. Why? 4. When ethanoic acid is dissolved in water, it turns the litmus paper red. Why?


59

Chapter 7: Acid and Bases B. Studying the chemical properties of acids Objective: To study the chemical properties of acids Apparatus: 10 cm3 beaker, microspatula, filter funnel, retort stand and clamp, micro

burner, 25 cm3 conical flask, test tube, filter paper, wire gauze, microtripod stand, microcrucible, 10 cm3 measuring cylinder.

Materials: Copper(II) oxide, CuO powder, zinc powder, 1 mol dm-3 sulphuric acid, 2

mol dm-3 nitric acid, HNO3, 2 mol dm-3 hydrochloric acid, HCl, calcium carbonate, CaCO3, lime water, wooden splinter and filter paper.

I. Reactions of acids with bases

Figure 7.2

60

Procedure:

1. Pour about 5 cm3 of 1 mol dm-3 sulphuric acid, into a 10 cm3 beaker. Warm the acid with a microburner (refer to pg 11, Chap 1).

2. Use a microspatula to add copper(II) oxide powder bit by bit into the acid. Stir the mixture well.

3. Continue adding copper(II) oxide until some of it no longer dissolves. 4. Remove the unreacted copper(II) oxide by filtration. 5. Pour the filtrate into a microcrucible. Gently heat the salt solution to produce a

saturated solution. 6. Cool the saturated solution until crystals are formed. 7. Filter out the copper(II) sulphate crystals. Examine the crystals and record your

observations in your notebook. Data and observations:

Test on acid Observation Inference

Heating with copper(II) oxide

Questions:

1. How do you know that an acid-base reaction has occurred? 2. How is the product of the reaction obtained? 3. What are the products of the reaction? Write an equation for the reaction. 4. Complete the following,

Acid + Base ___________ + ___________

61

II. Reactions of acids with metals

Figure 7.3

Procedure:

1. Pour 5 cm3 of 2 mol dm-3 hydrochloric acid into a 10 cm3 beaker. Warm the acid with a microburner.

2. Use a microspatula to add zinc powder bit by bit into the acid. Stir the mixture well.

3. Test the gas produced by using a lighted splinter. 4. Continue adding zinc powder until some of it no longer dissolves. 5. Remove the unreacted zinc powder by filtration. 6. Pour the filtrate into a microcrucible. Gently heat the salt solution to produce a

saturated solution. 7. Cool the saturated solution until crystals are formed. 8. Filter out the zinc sulphate crystals. Examine the crystals and record your

observations in your notebook.



Test with zinc powder

62

Questions:

1. How do you know that the acid has reacted with the metal? 2. What is the lighted splinter for? 3. What is the salt and gas produced in the reaction? Write a balanced equation for

the reaction between hydrochloric acid, HCl and zinc. 4. Complete the following.

Acid + Metal __________ + __________ III. Reactions of acids with metal carbonates


1. Pour 5 cm3 of 2 mol dm-3 nitric acid into 10 cm3 beaker. Warm the acid with a microburner.

2. Add calcium carbonate into the acid with a microspatula. 3. Continue adding calcium carbonate until some of it no longer dissolves. 4. Remove the unreacted calcium carbonate by filtration. 5. Pour the filtrate into a microcrucible. Gently heat the salt solution to produce a

saturated solution. 6. Cool the saturated solution until crystals are formed. 7. Filter out the calcium nitrate crystals. Examine the crystals and record your

observations in your notebook.

63



Test with calcium carbonate

Questions:

1. Write an equation for the reaction between nitric acid and calcium carbonate. What are the products formed?

2. Complete the following.

Acid + Carbonate __________ + ___________ + ___________


64

Chapter 7: Acid and Bases C. Studying the chemical properties of bases Objective: To study the chemical properties of bases Apparatus: Comboplate, 10 cm3 beaker, microspatula, filter funnel, microburner, 25

cm3 conical flask, test tube, filter paper, wire gauze, microtripod stand, microcrucible, 10 cm3 measuring cylinder.

Material: 1 mol dm-3 sodium hydroxide, NaOH solution, benzoic acid powder,

ammonium chloride, NH4Cl powder, iron(II) sulphate, FeSO4 solution, litmus paper.

I. Reactions of bases with acids

Figure 7.5

Procedure: 1. Pour about 5 cm3 of 1 mol dm-3 sodium hydroxide solution into a 10 cm3 beaker. 2. Use a microspatula to add benzoic acid powder bit by bit into the acid. Stir the mixture well.

65

3. Continue adding benzoic acid until some of it no longer dissolves. 4. Remove the unreacted benzoic acid by filtration. 5. Pour the filtrate into a microcrucible. Gently heat the salt solution with a microburner

(refer to pg 11, Chap 1) to produce a saturated solution. 6. Cool the saturated solution until crystals are formed. 7. Filter out the sodium benzoate crystals. Examine the crystals and record your observations in your notebook. II. Reactions of bases with ammonium salts

Figure 7.6 Procedure: 1. Fill one third of well F1 of the comboplate with sodium hydroxide solution. 2. Add a microspatula of ammonium chloride powder in the well. 3. Test the gas formed using moist red litmus paper. 4. Observe what happen to the litmus paper. III. Reactions of bases with metal ions Procedure: 1. Add 10 drops of iron(II) sulphate solution into the well F2 of the comboplate. 2. Add 1 drop of sodium hydroxide solution into the well. Observe what happen. Data and observations:

Test on sodium hydroxide

Observation Inference

With benzoic acid powder added

66

Heating with ammonium chloride powder

With iron(II) sulphate solution


67

Chapter 7: Acid and Bases D. Measuring the pH of solutions used in daily life Objective: To measure the pH of solutions used in daily life Aparatus: Comboplate, thin stemmed propettes, microspatula. Materials: Vinegar, lemon juice, soap solution, distilled water, carbonated drink, tap water, rainwater, dilute hydrochloric acid, HCl and dilute sodium hydroxide, NaOH solution, universal indicator solution 1 2 3 4 5 6 7 8 9 A B C D E


1. Add 10 drops of vinegar to well A1. 2. Add 10 drops of lemon juice to well A2. 3. Add 10 drops of soap solution to well A3. 4. Add 10 drops of distilled water to well A4. 5. Add 10 drops of carbonated drink to well A5. 6. Add 10 drops of tap water to well A6. 7. Add 10 drops of rainwater to well A7. 8. Add 10 drops of dilute hydrochloric acid to well A8. 9. Add 10 drops of dilute sodium hydroxide to well A9.

Vinegar Lemon juice

Soap solution

Distill-ed water

Carbona-ted drink

Tap water

Rain water

Dilute HCl

Dilute

NaOH

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10. Add 1 drop of universal indicator solution into each of the wells, A1 to A9. 11. Stir the solution in each well with a clean plastic microspatula. 12. Observe the pH of all the solutions and record your observations in the table.

Data and observations:

Well Number Colour of solution Proposed pH

A1 (Vinegar) A2 (Lemon juice) A3 (Soap solution) A4 (Distilled water) A5 (Carbonated drink) A6 (Tap water) A7 (Rain water) A8 (HCl) A9 (NaOH)

Conclusions: References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya. 2. Bell, B. & Bradley, J.D. (2002). Advanced learning packages, Microchemistry experiences, Magister-Press Publishing House: Moscow.

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Chapter 7: Acid and Bases E. Determining the end point of the titration between hydrochloric acid, HCl and sodium hydroxide, NaOH solution using an acid-base indicator. Objective: To determine the end point of the titration between hydrochloric acid, HCl and sodium hydroxide, NaOH solution using an acid-base indicator Apparatus: 1 x comboplate, 1 x microstand, 2 x microburette, 1 x syringe, 1 x microspatula, 1 x silicone tube, propettes and white paper. Materials: 0.100 mol dm-3 hydrochloric acid, HCl, 0.1 mol dm-3 sodium hydroxide,

NaOH, phenolphthalein solution.

Figure 7.8

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Procedure: 1. Assemble the microburette as shown. Push the plastic microstand into well D2 of the

comboplate. Orient the pairs of arms on the central stem of the microstand so that one arm of each pair is directly above well F1. Clip the assembled microburette into each arm of the microstand above well F1.

2. Put the comboplate on a piece of white paper. 3. Rinse the 2 cm3 microburette with the sodium hydroxide solution in the following

way: (i) Set up the microburette as in Figure 7.8 by attaching the plastic

syringe to the top of the 2 cm3 microburette using silicone tubing. Place the plastic tip at the other end of the microburette.

(ii) Rinse the microburette with sodium hydroxide. Use the syringe to fill up the microburette through the plastic tip. Repeat this rinsing process twice.

4. Fill the rinsed microburette with exactly 1.00 cm3 of the sodium hydroxide solution.

Dispense all this solution into well F1 of the comboplate. Repeat this step twice, dispensing the 1.00 cm3 aliquots of sodium hydroxide into wells, F2 and F3.

5. Empty the microburette, rinse it with water. 6. Rinse the microburette at least three times with the hydrochloric acid, HCl.

7. Fill the microburette with the HCl to the 0.00 cm3 level (or there about). Read the

level of the meniscus and record this as the initial volume of HCl (titration 1). 8. Use the thin stemmed propette to add one drop of phenolphthalein solution to the

NaOH in the well F1. 9. Position the microburette above the comboplate so that the tip of the microburette is

above well F1. Note: Do not place the microburette too close to well F1 as the plastic microspatula may knock against it during stirring of the solution in the well. This may cause drops of the solution to splash out of the well.

10. Push down gently on the syringe plunger and add one drop of HCl into well F1. Stir the solution in well F1 with plastic microspatula. Be careful not to spill any solution out of the well. Leave the microspatula in the well during the titration.

11. Continue to add HCl from the microburette one drop at a time until the indicator changes colour from pink to colourless. Stir the solution in well F1 after each drop is added.

12. Observe the volume of HCl in the microburette and record this as the final volume.

Calculate the volume of HCl dispensed.

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13. Refill the microburette with the HCl and record the initial volume (Titration 2). 14. Add one drop of phenolphthalein indicator to the NaOH in well F2. Position the

microburette above well F2 by moving the plastic microstand to another small well in the D row of the comboplate.

15. Now, that you know the approximate volume of the HCl required to titrate the NaOH,

you can add the HCl a little more quickly than before until about 0.04 cm3 before the expected end point. Stir thoroughly.

16. Add the HCl slowly, one drop at a time with stirring, until the indicator changes from

pink to colourless. Record the final volume (Titration 3). 17. Repeat the titration in well F3.

Note: Reject any results where the end point has been overshot.

Data and observations:

Titration No. 1

2 3

Volume

of HCl/ cm3

Final burette reading (cm3)

Initial burette reading (cm3)

Volume of hydrochloric acid, HCl needed (cm3)

Average volume of HCl used: Conclusions:

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Questions:

1. a) What is the average volume of HCl needed to neutralize 25.0 cm3 of NaOH? b) Write the equation for the neutralization reaction.

2. a) How is the end point of the titration determined? b) How else could you determine the end point?

3. Explain the following: a) A clean burette has to be rinsed with a little acid before filling it up. b) There must be no air bubbles in the tip of the burette. c) Burette readings must be taken at eye level. d) There is no need to rinse the conical flask with NaOH.

References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya. 2. Bell, B., Akoobhai, B. & Bradley, J. (2005). RADMASTE microtitration experiments. Manual for secondary school learners. The UNESCO Associated Centre for Microscience Experiments.

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Chapter 8: Salts A. Solubility of nitrate, sulphate, carbonate and chloride salts. Objective: To study the solubility of nitrate, sulphate, carbonate and chloride salts. Apparatus: Comboplate, syringe, microspatula. Materials: Lead(II) nitrate, Pb(NO3)2, copper(II) nitrate, Cu(NO3)2, magnesium

nitrate, Mg(NO3)2, zinc nitrate, Zn(NO3)2, calcium nitrate, Ca(NO3)2, copper(II) sulphate, CuSO4, zinc sulphate, ZnSO4, barium sulphate, BaSO4, magnesium sulphate, MgSO4, lead(II) sulphate, PbSO4, calcium sulphate, CaSO4,copper(II) carbonate, CuCO3, zinc carbonate, ZnCO3, potassium carbonate, K2CO3, sodium carbonate, Na2CO3, ammonium carbonate, magnesium carbonate, MgCO3, copper(II) chloride, CuCl2, zinc chloride, ZnCl2 and mercury chloride, HgCl2, magnesium chloride, MgCl2 lead(II) chloride, PbCl2 and silver chloride, AgCl.

Procedure:

Figure 8.1

1. Use a spooned end of a plastic microspatula to place 2 leveled spatulas of lead(II) nitrate powder into well F1 of the comboplate.

2. Use a syringe to add 1 cm3 of distilled water to the well F1. Stir the mixture and note the solubility of the salt.

3. Repeat steps 1 and 2 using copper(II) nitrate, magnesium nitrate, zinc nitrate, calcium nitrate, copper(II) sulphate, zinc sulphate, barium sulphate, magnesium sulphate, lead(II) sulphate, calcium sulphate, copper(II) carbonate, zinc carbonate, potassium carbonate, sodium carbonate, ammonium carbonate, magnesium carbonate, copper(II) chloride, zinc chloride, mercury chloride, magnesium chloride, lead(II) chloride and silver chloride.

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Data and Observations: Type of salt Salt Solubility

Nitrate

Lead(II) nitrate Copper(II) nitrate Magnesium nitrate Zinc nitrate Calcium nitrate

Copper(II) sulphate Zinc sulphate Magnesium sulphate

Sulphate Barium sulphate Lead(II) sulphate Calcium sulphate

Copper(II)chloride Zinc chloride Magnesium chloride

Chloride Mercury chloride Lead(II) chloride Silver chloride

Potassium carbonate Sodium carbonate Ammonium carbonate

Carbonate Copper(II) carbonate Zinc carbonate Magnesium carbonate


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Chapter 8: Salts B. Preparation of soluble salts by mixing acids with bases Objective: To prepare soluble salts by mixing acids with bases Apparatus: Comboplate, microstand, micro crossarms, microburette, pipette tip,

silicone tube, syringe, microspatula, propette, conical flask 10 ml, microcrucible, microburner, microtripod stand, wire gauze.

Materials: 2 mol dm-3 hydrochloric acid, HCl, 2 mol dm-3 potassium hydroxide,

KOH, phenolphthalein. Procedure: I. To determine the volume of acid for neutralization

Figure 8.2

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1. Use the microburette to transfer 2.0 cm3 of potassium hydroxide solution to a conical flask. Use the propette to add one or two drops of phenolphthalein.

2. Push the plastic microstand into well D1 of the comboplate. Orient the pairs of arms on the central stem of the microstand so that one arm of each pair is directly above the conical flask.

3. Fill the burette with hydrochloric acid, HCl and record the initial burette reading. 4. Titrate carefully by slowly adding the acid into the conical flask and shake well. 5. Continue adding the acid until the indicator just turns from pink to colorless.

Record the final burette reading. 6. Determine the volume of acid used to neutralize 2.0 cm3 of the base. (Let the

volume be V cm3). II. Preparation of the salt

Figure 8.3

1. Use a microburette to transfer 2.0 cm3 of the same potassium hydroxide solution into a 10 cm3 conical flask. Do not add any indicator.

2. From the microburette, add exactly V cm3 of hydrochloric acid to the base and shake well.

3. Pour the contents of the conical flask into a microcrucible. 4. Gently heat the solution to evaporate most of the water to produce a saturated

solution with a microburner. 5. Cool the hot saturated salt solution for crystallization to occur. 6. Filter to obtain the potassium chloride crystals.

III. Recrystallisation of the salt.

1. Place the potassium chloride crystals in a 10 cm3 beaker. 2. Add just enough distilled water to cover the crystals. Gently heat the solution and

stir with a microspatula. 3. Filter to remove impurities and pour the filtrate into a microcrucible.

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4. Gently heat the solution to obtain a saturated salt solution with a microburner. 5. Cool the hot saturated solution to allow it to crystallize. 6. Filter and press the crystals with a few pieces of filter paper to dry them. 7. Study the physical properties of the crystals and record your observations in your

notebook. Data and Observations: Conclusions: Questions:

1. How do you know when the salt solution is saturated? 2. Write the chemical equation for the reaction to obtain KCl crystals. 3. Name another salt that can be prepared from the reaction between an acid and a

base.


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Chapter 8: Salts C. Preparation of soluble salts by mixing an acid with an insoluble metal oxide Objective: To prepare soluble salts by mixing an acid with an insoluble metal oxide Apparatus: 10 cm3 beaker, microspatula, filter funnel, microburner, 25 cm3 conical

flask, filter paper, wire gauze, microtripod stand, microcrucible, 10 cm3 measuring cylinder.

Materials: 2 mol dm-3 sulphuric acid, H2SO4 and copper(II) oxide, CuO powder. Procedure:

Figure 8.4

1. Pour 5 cm3 of 2 mol dm-3 sulphuric acid into a 10 cm3 beaker. Warm the acid with a microburner (refer to pg 11, Chap 1).

2. Use a microspatula to add copper(II) oxide powder bit by bit into the acid. Stir the mixture well.

3. Continue adding copper(II) oxide until some of it no longer dissolves. 4. Remove the unreacted copper(II) oxide by filtration. 5. Pour the filtrate into a microcrucible. Gently heat the salt solution to produce a

saturated solution.

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6. Cool the saturated solution until crystals are formed. 7. Filter out the copper(II) sulphate crystals. 8. Carry out a crystallization to obtain pure copper(II) sulphate crystals. 9. Study the physical properties of the crystal and record your observation in your

notebook.

Data and Observations: Conclusions: Questions:

1. Give the equation for the reaction between HNO3 and copper(II) oxide. 2. Name another salt that can be prepared from the reaction between an acid and an

insoluble metal oxide. References: 1. Low, S.N., Lim, Y.C., Eng, N.H., Lim, E.W. & Ahmad, U.K. & Tan, L.L. (2005). Chemistry practical book form 4, Abadi Ilmu Sdn. Bhd: Petaling Jaya.

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Chapter 8: Salts D. Preparation of insoluble salts by carrying out a precipitation reaction Objective: To prepare insoluble salts by carrying out a precipitation reaction Apparatus: 10 cm3 beaker, microspatula, 25 cm3 conical flasks, filter funnel, filter

paper and syringe. Materials: 0.5 mol dm-3 lead(II) nitrate, Pb(NO3)2, potassium iodide, KI, potassium

chromate(IV), K2Cr2O7, sodium sulphate, Na2SO4, and barium chloride, BaCl2 solution.

Procedure: I. Preparation of lead(II) iodide

Figure 8.5

1. Add about 0.5 cm3 of 0.5 mol dm-3 lead(II) nitrate solution and 0.5 cm3 of 0.5 mol dm-3 potassium iodide solution in a 10 cm3 beaker. 2. Stir the mixture thoroughly with a microspatula. A yellow precipitate forms

immediately. 3. Filter the mixture to obtain the yellow lead(II) iodide as the residue. 4. Rinse the residue with distilled water to remove any traces of other ions in it. 5. Dry the yellow residue by pressing it between two pieces of filter paper.

II. Preparation of lead(II) chromate(VI)

1. Add about 0.5 cm3 of 0.5 mol dm-3 lead(II) nitrate solution and 0.5 cm3 of 0.5 mol dm-3 potassium chromate(VI) solution in a 10 cm3 beaker.

2. Stir the mixture thoroughly with a microspatula. A yellow precipitate forms immediately.

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3. Filter the mixture to obtain the yellow lead(II) chromate(VI) as the residue. 4. Rinse the residue with distilled water and dry it between two pieces of filter

paper. III. Preparation of barium sulphate

1. Add about 0.5 cm3 of 0.5 mol dm-3 barium chloride solution and 0.5 cm3 of 0.5 mol dm-3 sodium sulphate solution in a 10 cm3 beaker.

2. Stir the mixture thoroughly with a microspatula. A white precipitate forms immediately.

3. Filter the mixture to obtain the white barium sulphate as the residue. 4. Rinse the residue with distilled water and dry it between two pieces of filter

paper. Data and Observations: Conclusions: Questions:

1. Give the equations for the preparation of the three salts. 2. Can this kind of reaction be used prepare NH4Cl? Give reasons for your answer. 3. PbCrO4 cannot be purified by recrystallisation. Why?


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Chapter 8: Salts E. Constructing the ionic equation for the formation of lead(II) chromate(VI) Objective: To construct the ionic equation for the formation of lead(II) chromate(VI). Apparatus: Comboplate, Durham tubes, prestick/plasticine, microburette, syringe and

ruler. Materials: 0.5 mol dm-3 lead(II) nitrate, Pb(NO3)2 solution, 0.5 mol dm-3 potassium

chromate, K2Cr2O7 solution. Procedure:

Figure 8.6

1. Label seven Durham tubes of the same size from 1 to 7 and place them in the bigger wells of the comboplate.

2. Fill the syringe 0.5 mol dm-3 potassium chromate(VI) solution. Run in 0.5 cm3 of the potassium chromate(VI) solution into each of the seven Durham tubes.

3. Fill the microburette with 0.5 mol dm-3 lead(II) nitrate solution. Add 0.10, 0.20, 0.30, 0.40, 0.50, 0.60 and 0.70 cm3 lead(II) nitrate to each of the seven Durham tubes respectively.

4. Shake each Durham tube well. 5. Place all the tubes in the smaller wells of the comboplate vertically using

prestick/plasticine. 6. Leave it aside for about half an hour to allow the precipitate to settle. 7. Measure the height of the precipitate in each Durham tube.

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8. Note the colour of the solution above the precipitate in each tube. 9. Record your readings and observations in your notebook as shown in Table

below. 10. Plot a graph of precipitate height against volume of lead(II) nitrate solution.


Durham Tube 1 2 3 4 5 6 7 Volume of 0.5 mol dm-3 potassium chromate (VI) solution (cm3) 0.5 0.5 0.5 0.5 0.5 0.5 0.5

Volume of 0.5 mol dm-3 lead(II) nitrate solution (cm3) 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Height of precipitate (cm) Colour of solution above precipitate


1. Why must you have the volume of Pb(NO3)2 constant? 2. Why are different volumes of potassium chromate(VI) added to each test tube? 3. Why does the colour of the solution above the precipitate change? 4. How does the height of the precipitate formed change? Why?


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Chapter 8: Salts F. Carrying out chemical tests to identify gases Objective: To carry out chemical tests to identify gases. Apparatus: Comboplate, silicone tube, lid 1, lid 2, syringe, microspatula, glass rod,

W-tube, microburner, combustion and fusion tube, toothpick, propette, forceps.

Materials: Manganese dioxide, MnO2 powder, fresh hydrogen peroxide solution,

H2O2 (10%), 2 mol dm-3 sulphuric acid, H2SO4, zinc, Zn powder, calcium carbonate, CaCO3 powder, dilute hydrochloric acid, HCl, lime water, dilute sodium hydroxide, NaOH solution, ammonium chloride, NH4Cl powder, household bleach solution, 2 mol dm-3 hydrochloric acid, HCl, sodium chloride, NaCl powder, concentrated sulphuric acid, H2SO4, concentrated ammonia, NH3, dilute acidified potassium manganate(VII), KMnO4 solution, sodium sulphate, Na2SO4 powder, lead(II) nitrate, Pb(NO3)2 powder.

Procedure: I. Test for oxygen gas, O2

Figure 8.7

1. Use the spooned end of a plastic microspatula to place one leveled spatula of manganese dioxide powder into well F1 of the comboplate.

2. Seal the well securely with lid 1.

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3. Attach a piece of silicone tubing to the tube connector on lid 1 so that it slants away from the syringe inlet.

4. Connect the free end of the silicone tube to the glass combustion tube as shown in Figure 8.6.

5. Fill the syringe with 0.5 cm3 of freshly prepared 10% hydrogen peroxide solution. 6. Fit the syringe into the syringe inlet on lid 1, but do not add the hydrogen

peroxide to the well yet. 7. Light the microburner (refer to pg 11, Chap 1) and put it down away from the

comboplate. 8. Take the toothpick and hold the narrow end of the splint in the flame of the

microburner until it begins to burn. 9. While the top 1 to 2 cm of

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