Sci(Chem)MCQ (Caa30 Apr 2012) With Answers

7/29/2019 Sci(Chem)MCQ (Caa30 Apr 2012) With Answers

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1. A bottle of copper(II) oxide had been contaminated with some solid sodiumchloride. How can the sodium chloride be removed from the copper(II)oxide?

A Heat the mixture and allow it to coolB Add dilute acid to the mixture and filter

C Add aqueous silver nitrate to the mixtureD Add water to the mixture and filter

Thinking process: This question is linked to the topic Separation Techniques. You need to

analyse the mixture given and the properties of the constituents in themixture.

In the above mixture, which is made up of 2 solids, you should be able todifferentiate the 2 substances based on their solubility in water, as sodium

chloride is a soluble salt while copper(II) oxide is an insoluble base. Afterknowing the properties, you can then proceed to choose the appropriatemethod, which in this case is filtration.

2. Which of the following is likely to be a pure compound?

A A white powder which dissolves in waterB Green crystals which melt at 58oCC Blue crystals which melt over the range of 55oC and 60oCD A liquid which gives two fractions when distilled

Thinking process:

This question is assessing your understanding of the concept purecompound. A pure substance is made up of ONLY one substance and italways has a fixed melting point and boiling point.

St Hildas Secondary SchoolSecondary Four Express / Five Normal AcademicScience (Chemistry) 5116 / 5118Remedial Worksheet for Term 2 Week 6

50


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3. A sugar, raffinose was treated with dilute hydrochloric acid. Theresulting solution, Y, together with some known sugar solutions forreference, was analysed by chromatography. The following

chromatogram was obtained.

This evidence suggests that dilute hydrochloric acid breaks downraffinose into

A Glucose and maltose

B Glucose, galactose and fructoseC Glucose, maltose and fructoseD Glucose, galactose and one sugar not among the reference

sugars

Thinking process:

This question is assessing your understanding of chromatography and howto read/interpret a chromatogram. In this chromatogram, the spot for theunknown sample is located on the LHS, while the reference/known

substances are on the RHS. You need to match the spots from the separation of the unknown sample to

the known substances by drawing horizontal lines across. Identical dyesproduce spots at the same height, when the same solvent is used.

4. On warming a salt with excess aqueous sodium hydroxide, a gas thatturned damp red litmus paper blue was given off. On adding aluminiumfoil to the boiled solution, a further evolution of the same gas occurred.

What was the salt?

A Sodium nitrateB Ammonium chlorideC Ammonium sulphateD Ammonium nitrate

Y glucose maltose galactose fructose


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5. The outer shell electrons in the compound YZ2 are shown.Use the Periodic Table to find the number of neutrons in atom Y, which

is in the Period Li to Ne.

A 6B 8C 10D 12

Thinking process:

This question is linked to the topic Atomic Structure and ChemicalBonding. The focus is on the atom Y. From the diagram, you willobserve that atom Y has 6 valence electrons. This means it is in GroupVI, a non-metal.

Based on all the information given in the question, we know that atom Yis in Group VI and found in Period 2. This could only mean that Atom Y

is Oxygen. Remember that number of neutrons can be determined bytaking the difference between mass number and proton number.

6. P2Q3 is an ionic compound.Which statement about P2Q3 is correct?

A It conducts electricity when molten due to free moving electronsB It conducts electricity when molten because its ions are able to

move.C It has low melting point.D Its ions are P2+ and Q3-.

Thinking process:This question is linked to the topic Chemical Bonding Ionic Bonding.Here, you are required to recall the properties of ionic compounds. In otherwords, ionic compounds have high melting and boiling points (because large

amount of energy required to overcome the strong electrostatic forces ofattraction), conduct electricity when molten or dissolved in water (becausewhen in molten state or dissolved in water the ions are mobile and can act ascharge carriers)and mostly soluble in water.

Please also note that since the chemical formula of the compound above isP2Q3, the ions present are P

3+ and Q2- respectively. (Hence, Option D is

X

X

X

X

X

X

XX

X

Z

X

X

X

XX

Z

Y

Key:

- electrons ofY

x - electrons ofZ


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7. The formula for the aluminium ion is Al3+.It follows that this ion has

A three electrons in its outer shellB three more protons than electronsC three more electrons than protonsD three more neutrons than electrons

Thinking process:This question is linked to the topic Atomic Structure. Since the ion formed isa positive one, we know that number of protons is more than electrons.Neutrons are not affected in the formation of ion.

8. The main ore of zinc is zinc blende, ZnS (Mr = 97). When this ore isheated in air, the reaction is represented by the following equation.

2ZnS + 3O2 2ZnO + 2SO2

What volume of oxygen at room temperature and pressure would beneeded to react completely with 194g of ZnS?

A 3 dm3

B2

243dm3

C 3 24 dm3

D 3 32 dm3

Thinking process:This question is linked to the topic Chemical Calculations.

1st

step: Calculate the number of moles of ZnS, using the formula:Number of moles = mass / molar mass2nd step: Compare the mole ratio between ZnS and Oxygen. Based on the moleratio, determine the number of moles of oxygen.3rd step: Volume of gas = number of moles x 24 dm3

9. Fluorine is the first element in Group VII of the Periodic Table.Which statement about fluorine is NOT correct?

A It forms ionic compounds with metalsB It is a gas at room temperature and pressureC It is a more powerful oxidizing agent than chlorineD It is monoatomic at room temperature

Thinking process:


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10. Air polluted by sulphur dioxide was passed through the apparatusshown in the diagram.

Which of the following solutions could be used as Z to show thepresence of sulfur dioxide?

A Aqueous potassium iodideB Aqueous iron(II) sulphate

C Acidified potassium dichromate (VI)D Limewater

Thinking process:This question is linked to the topic Oxidation and Reduction / QualitativeAnalysis. Sulfur dioxide gas can act as a reducing agent, where it will reducean oxidizing agent such as acidified potassium dichromate (VI).Observation: The orange colour solution of acidified potassium dichromate (VI)changes to green in the presence of sulfur dioxide (reducing agent).

11. The reaction between aqueous sodium hydroxide and hydrochloric acidis exothermic.

Which graph shows that the change in temperature when aqueoussodium hydroxide is added to hydrochloric acid until the alkali ispresent in excess?

oC

Volume of sodium hydroxide

A

Volume of sodium hydroxide

o

CB


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Thinking process:This question is linked to the topic Heat Changes in Reaction.As neutralization reaction is an exothermic reaction, heat will be released andthis is represented by the rise in temperature. However, the increase intemperature will stop once the reaction is completed and the temperature willthen try to match back to the surrounding.

12. Oxides of elements may be classified as acidic, basic or amphoteric.Which set of oxides is correctly classified?

Acidic Basic AmphotericA Carbon dioxide Copper(II) oxide Zinc oxide

B Carbon dioxide Zinc oxide Copper(II) oxideC Copper(II) oxide Carbon dioxide Zinc oxideD Zinc oxide Copper(II) oxide Carbon dioxide

Thinking process:This question is linked to the topic Acids and Bases (Types of Oxides)You are required to memorise the definition of acidic, basic and amphotericoxides.

Acidic oxides are oxides of non-metals which dissolves in water to forman acid.

Basic oxides are oxides of metals which are usually insoluble in water,except for sodium oxide and potassium oxide. Basic oxides react withacids to form salt and water.

Amphoteric oxides are made up of special group of oxides of metals,mainly Zinc Oxide, Aluminium oxide and Lead (IV) oxide, which reactwith both acids and alkalis to form salt and water.

13. In which process is energy released to the surroundings?

A Dissolving ammonium nitrate in waterB Thermal decomposition of copper(II) carbonateC Reacting sulphuric acid with sodium hydroxideD Melting ice

Thinking process:

This question is linked to the topic Heat changes in reaction.You are required to memorise the list of exothermic and endothermic reactionsgiven by your teacher in class. In this question, the focus of question is onexothermic, since energy is released to the surroundings.Option A endothermicOption B endothermic, as heat is absorbed to break down the compound intosimpler substances ( i e decomposition)


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14. Two solutions are mixed in a beaker and the mass of the beaker andthe contents is then recorded at various times. The graph shows the

results.

Which could be the two solutions?

A aqueous copper(II) sulphate and aqueous ammoniaB aqueous sodium carbonate and dilute nitric acidC aqueous sodium hydroxide and aqueous zinc sulphateD dilute hydrochloric acid and aqueous sodium sulphate

Thinking process:This question is assessing your understanding of Speed of Reaction.Based on the shape of the graph, you know that the graph is obtained bymeasuring the mass of system over time. This method is best applied toreactions which produce gas as one of the products, which results in adecrease in mass, as the gas produced will be given off.

15. Which products are formed when dilute hydrochloric acid reacts withthe substances shown in the table?

substance productsA iron iron(II) chloride + hydrogen onlyB iron(II) carbonate iron(II) chloride + carbon dioxide gas onlyC iron(II) oxide iron(II) chloride + oxygen gas onlyD iron(II) sulphate iron(II) chloride + sulphur dioxide only

Thinking process:This question is linked to the topic Acids: Reactions of Acids.Iron is a metal and will react with acid to produce salt and hydrogen gas. Sincethe acid used is hydrochloric acid, the salt produced is a chloride.

16. A chemical reaction between a solid and an acid is too fast for safe useb l f t d t Whi h t f h i t lik l t k th

Mass of

beaker and

contents

time


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Thinking process:This question is linked to the topic Speed of Reaction: Factors affectingspeed of reaction. In order to increase speed of reaction, you can use solidswith larger surface area (i.e powdered form), higher concentration of reactants,higher temperature, higher pressure (only for gases) and also may usecatalysts.

17. Which of the following is correct about air?

A It contains 79% oxygen and 20% nitrogen.B It is a mixture of elements.

C It contains carbon dioxide from incomplete combustion ofcarbon-containing substances.

D It is a mixture of elements and compounds.

Thinking process:This question is linked to the topic Atmosphere and Environment. It can alsobe viewed as a General Knowledge question about air. Air is a mixture ofelements and compounds (eg: oxygen gas (element) and carbon dioxide(compound)), it is made up of 79% of nitrogen, 20% of oxygen and 1% of other

gases with argon as the main constituent and carbon dioxide.

18. The equations show four reactions which take place in the blastfurnace during the extraction of iron from haematite.

C + CO2 2CO (1st)

CaCO3 CaO + CO2(2nd)

Fe2O3 + 3CO 2Fe + 3CO2 (3rd)

SiO2 + CaO CaSiO3 (4th)

How many of these are redox reactions?

A 1 B 2 C 3 D 4

Thinking process:This question is linked to the topic Extraction of Iron and also Redox.

By definition, redox reactions involve oxidation and reduction reactions takingplace at the same time.

1st: Redox ReactionThe element carbon has undergone both oxidation and reduction in the abovereaction. This is because its oxidation has changed from 0 to +2 (oxidized) andalso +4 to +2 (reduced)

d


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19 A student wants to titrate aqueous potassium hydroxide with dilute nitricacid. Which two pieces of apparatus is not required for the titration?

A P and R

B P and S

C Q and R

D Q and S

Thinking process: This question is linked to Preparation of Salts and yourknowledge about apparatus and their functions. P = Burette (to measurevolume of liquids up to 0.1cm3 accuracy), Q = Fractionating Column packedwith beads, R = pipette (measure fixed volumes of liquids), S = Liebig

condenser.

20 An element X has the electronic structure 2, 4. The simplest compoundformed when X combines with hydrogen is most likely to be a

A compound that conducts electricity when aqueous.

B compound with a low boiling point.

C molecule made up of four atoms.D solid compound which conducts electricity.

Thinking process:This question is linked to the topic Atomic structure and Chemical Bonding.From the electronic structure 2 4 you will know that Element X is a non-metal

P Q R S


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21 When aqueous sodium hydroxide is added to salt X, the white precipitateformed remains insoluble in excess aqueous sodium hydroxide.(This is a cation test for Salt X. Since white ppt is formed and

insoluble in excess, we can deduce it to be Ca2+

.)

A fresh portion of salt X is dissolved in water and added to acidifiedbarium nitrate, white precipitate is formed.(This is an anion test for sulfate. Since it is a positive test, Salt Xcontain sulfate.)

What could X be?

A calcium chloride

B calcium sulfate

C lead(II) chloride

D lead(II) sulfate

22 Element X has a proton number of 15. Element Y has a proton numberof 9. Which statement about the compound formed from X and Y iscorrect?

Thinking process:This question is linked to the topic Atomic structure and ChemicalBonding. You are required to write out the electronic configuration forElement X and Y respectively in order to help you determine the type ofbonding present.

Element X = 2.8.5 (Group V, since there are 5 valence electrons). Thus,one atom of X will share 3 of its 5 valence electrons.Element Y = 2.7 (Group VII, since there are 7 valence electrons). Thus,one atom of Y will share one of its 7 valence electrons.

Hence, an atom of X will combine with 3 atoms of Y, forming a compoundwith chemical formula of XY3.

A The compound is a covalent compound with the formula XY3.

B The compound is a covalent compound with the formula X3Y.

C The compound is an ionic compound with the formula XY3.

D The compound is an ionic compound with the formula X3Y.


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23 The equation for the reaction between hydrogen sulfide and chlorine isgiven below.

H2S (g) + Cl2 (g)

S(s) + 2HCl (g)

Thinking process:This question is linked to the topic Oxidation and Reduction.From the equation above, you would observe that H2S has been oxidized(hence, it is acting as a Reducing Agent) while Cl2 has been reduced(hence, it is acting as an Oxidising Agent).

Which of the following statements is correct?

A Cl2 is the oxidising agent. It adds electrons to H2S.

B Cl2 is the reducing agent. It removes electrons from H2S.

C H2S is the reducing agent. Cl2 is reduced.

D It is not a redox reaction.

24 Which of the following gives the correct classification for the four oxidesbelow?

Thinking process:This question is linked to the topic Acids and Bases Types of Oxides)Please refer to Question 12 for explanation.

CO2 Li2O NO PbO

A basic acidic acidic amphoteric

B basic amphoteric acidic basic

C acidic basic neutral amphoteric

D acidic neutral neutral basic

25 In which equation is the sign of the energy change, H, shown correctly?Thinking process:This question is linked to Heat Changes in Reactions.

A positive value for H represents an endothermic reaction while anegative value for H represents an exothermic reaction.


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26 Which one of the following would give a pH of less than 7 whendissolved in water?Thinking process:

This question is linked to the topic Acids and Bases.Since the question is looking for a substance which would give a pH ofless than 7 when dissolved in water, you should think of acidicsubstances. In other words, the substance must produce H+ ions whendissolved in water.

A ammonia

B hydrogen chloride

C potassium nitrateD sodium chloride

27 Which of the following salts can be prepared by titration?Thinking process:This question is linked to the topic Preparation of SaltsTitration method is used to prepare soluble salts of sodium, potassiumand ammonium only.

Note: Titration can also be used to prepare Group I salts. A ammonium sulfate

B calcium sulfate

C copper(II) carbonate

D zinc chloride


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28 Dissolving ammonium chloride in water is endothermic.

Which graph shows the change in temperature with time until there is no

further change in temperature?

Thinking process:This question is linked to the topic Heat changes in Reaction.Since you are looking for endothermic reaction, the temperaturewill drop before rising to match the surrounding temperature again.

Temperature

room

temperature

roomtemperature

Temperature A

C

Time

Temperature B

TemperatureD

roomtemperature

roomtemperature

Time

TimeTime


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29 Which of these statements about the metals in Group I of the PeriodicTable is correct?Thinking process:This question is linked to the topic The Periodic Table: Group Ielements. You are required to be very familiar with the properties andtrends of Group I elements, or else known as Alkali Metals.These metals are known as Alkali metals as they react with water to formalkalis and hydrogen gas. For example,2Na (s) + 2H2O(l) 2NaOH (aq) + H2 (g)(Please avoid thinking that the product form is sodium oxide, NaO)This include, trends such as melting and boiling point decreases downthe group, the densities increases down the group and chemical reactivityincreases down the group.

A Their densities decrease down the group.

B Their melting points decrease down the group.

C Their reactivities decrease down the group.

D They react with cold water to give metal oxides and hydrogen gasonly.

30 The table below shows possible impurities in iron ore (haematite) andpossible substances which could be added to the blast furnace toremove such impurities. Which one of the following options is correct?

Thinking process:This question is linked to the topic Extraction of IronTo remove the impurities, which is mainly silicon dioxide (sand), calciumcarbonate (limestone) is decomposed to form basic oxide, calcium oxide.The basic oxide will react with acidic oxide, silicon dioxide to formcalcium silicate.

impurity in iron ore chemical added to remove impurity

A chalk acid

B clay slag

C granite cokeD sand (silica) limestone

31 Which of the following best explains why recycling ensures that metalswill be available in the future?


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32 The table below describes the reactions between 3 metals X, Y and Z

with cold water and steam.

reaction with cold water reaction with steam

X no reaction reacts slowly to formhydrogen gas

Y no reaction no reaction

Zreacts readily to formhydrogen gas

reacts violently to formhydrogen gas

Thinking process:This question is linked to the topic Reactivity series of metals.From the data in the table above, we can observe that the least reactive metalis Y, followed by X being moderately reactive and Z as highly reactive.

Which of the following are likely to be metal X, Y and Z?

X Y Z

A iron lead calcium

B lead copper magnesium

C zinc copper sodium

D zinc silver potassium

33 Which of the following statements about the molecules of cooking oil atroom temperature is correct?

Thinking process:This question is linked to the topic Kinetic Particle Theory.Since cooking oil is liquid at room temperature, we know that the particles areable to slide past one another and the particles are disorderly and not as closeas that of solids. The forces of attraction between the particles is less strongcompared to solids (even though the particles are still close together)

A The molecules vibrate about fixed positions.B The molecules are close together but in a disorderly

arrangement


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34 Which substance is wrongly matched with the type of particles it

contains?

Thinking process:This question is linked to the topic Elements, Compounds and Mixtures.

Ions charged particles formed from atoms.Molecules when 2 or more non-metals combined chemically by sharingelectrons.Atoms simplest form of matter.

Note:

HCl (g) is actually a covalent molecule

HCl (aq) is actually ionic when in aqueous state.Substance Type of Particles

A HCl (g) ions

B I2 (s) molecules

C LiBr (s) ions

D Graphite atoms

35 In which reaction is the underlined substance acting as a reducing agent?

Thinking process:

This question is linked to the topic Redox.Reducing agents are substances that will reduce others but itself isoxidized in the reaction.

A chlorine + iron(II) chloride iron(III) chloride

B hydrogen + copper(II) oxide copper + water

C hydrochloric acid + magnesium oxide magnesium chloride + water

D zinc oxide + carbon monoxide zinc + carbon dioxide


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36 Which of the following salts is incorrectly matched with its method ofpreparation?

Thinking process: This question is linked to the topic Preparation ofSalts. There are 3 main methods of preparation of salts:Method 1: For soluble salts not including sodium, potassium andammonium salts.

Reacting acids with excess metals (provided the metals are nothighly reactive and it becomes dangerous) / metal oxides/ metalcarbonates

Method 2: For preparation of sodium, potassium and ammonium salts.

Reacting acids with soluble bases (alkalis) Titration.

Method 3: For preparation of insoluble salts

Reacting 2 soluble salt solutions together.

Salt Method of Preparation

A silver nitrate add excess silver to warm dilute nitric acidB ammonium

sulphatetitrate aqueous ammonia with dilute sulphuricacid

C lead(II) chloride mix aqueous lead(II) nitrate and dilutehydrochloric acidD Iron(III) sulphate add excess iron(III) oxide to warm dilute

sulphuric acid

37 Which of the following process(es) give(s) out energy?

(I) condensation of ethanol vapour (give out energy)(II) melting of ice (energy is absorbed to overcome the forces ofattraction holding the particles in fixed arrangement)(III) reacting aqueous sodium hydroxide with dilute hydrochloric acid(neutralization, give out energy)

(IV) H2 H + H (From the equation, we can see that the moleculeof hydrogen is broken down to single atoms of Hydrogen, so energy mustbe taken in instead of giving out energy)

Thinking process:This question is linked to the topic Heat changes in reaction.Since the question stated gives out energy., we are looking forexothermic reactions such as neutralization, combustion etc.


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For questions 38 to 40 refer to this part of the Periodic Table.

O

Na Mg Al

K Ti Fe

38 What do the metals Fe (iron) and Ti (titanium) have in common?

Thinking process:This question is linked to the topic The Periodic Table.Fe and Ti are metals found in the centre block which means they aretransition metals. Key properties of transition metals include ability to exist invariable oxidation states and form coloured compounds and often used ascatalysts.

A They belong to the same group in the periodic table.B They form coloured compounds.C They do not conduct electricity.D They are resistant to corrosion.

39 When Fe (iron) and O (oxygen) react, iron atoms join with oxygenatoms to form iron oxide, Fe2O3. When this happens, . . .

Thinking process:This question is linked to the topic Chemical Bonding. Since iron atoms andoxygen atoms are chemically combined to form iron(III) oxide, we know acompound and a chemical reaction has taken place. During a chemicalreaction to form new products, there will be re-arrangement of atoms and sincethe compound formed is ionic in nature, electrons are transferred.

A the nuclei from iron and oxygen atoms join together.

B electrons are lost and new atoms form.C electrons are transferred and chemical bonds hold the atoms

together.D the nuclei are transferred and new atoms form.

40 Fe (iron) and O (oxygen) are in the periodic table but Fe2O3 (iron oxide)


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41 Which one of the following statements about the Periodic Table is nottrue?Thinking process:This question is linked to the topic The Periodic Table.Consider the Group trends and also the general structure of Periodic Tablewhen answering this question.

Key concepts:

Number of valence electrons corresponds to the Group numberof the element.

Number of electron shells corresponds to the Period in which theelement is in.

Moving from left to right, the elements change from metals,metalloids and non-metals.

A The elements in a group have the same number of outer shell

electrons

B The reactivity of the halogens decreases down Group VII.

C The melting points and densities increases down Group I.

D As we go across a period from left to right, the elements change from

metals to metalloids and then to non-metals.

42 Which row in the table correctly describes the type of combustion anda substance produced when fuel oil is burned in open air?

Thinking process:This question is linked to the concept of Combustion.

Complete combustion of fuels will result in two main products carbon dioxide and waterIncomplete combustion due to insufficient oxygen supply willresult in the following products carbon monoxide and unburntcarbon.

Type of combustion Substance producedA Complete Carbon

B Complete Carbon dioxideC Incomplete Carbon dioxideD Complete Carbon monoxide


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43 Note the following information about Titanium, Sodium and Carbon.

Titanium cannot be extracted by carbon reduction of its ore,

which contains titanium dioxide, TiO2. When sodium reacts with titanium chloride, titanium and sodium

chloride are formed. (Since Na is able to displace titanium fromits salt solution, Na is more reactive than Ti)

Sodium, not carbon, is used to extract titanium from itscompounds.

Thinking process:This question is linked to the concept of reactivity of metals with respectto carbon.

Which row in the table does this information suggest to be the order ofreactivity for carbon, sodium and titanium?

Most reactive Least reactiveA Sodium Titanium CarbonB Sodium Carbon Titanium

C Titanium Sodium CarbonD Carbon Titanium Sodium

44 Which one of the following equations does not represent a neutralizationreaction?

A 2HCl (aq) + Fe(OH)2(s) FeCl2(aq) + H2O (l)

B H2SO4 (aq) + Ba(NO3)2 (aq) BaSO4 (s) + 2HNO3 (aq)C H2SO4 (aq) + 2NH3 (g) (NH4)2 SO4 (aq)D 2HNO3 (aq) + Mg(s) Mg(NO3)2 (aq) + H2 (g)

Thinking process:This question is linked to the topic Acids and Bases

Please note that neutralization is describe the reaction between

hydrogen ions and hydroxide ions to produce water,H+ (from acids) + OH (from soluble bases)

H2O as neutralisation

In options A, C and D, the acids are behaving as acids, where the H+ions are used up during the reactions.

H f i B h id i b h i id h i


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45 Which hydroxide dissolves in water to form an alkaline solution?Since the question requires you to choose a base which is soluble,the best option is calcium hydroxide.

A Aluminium hydroxideB Calcium hydroxideC Copper (II) hydroxideD Iron (III) hydroxide

**46 All of the following substances produce carbon dioxide on completecombustion. Which one will produce 1.0 mole of carbon dioxide?

A 2.0 mole of graphite, C.B 1.5 mole of propane, C3H8.C 1.5 mole of ethane, C2H4.D 0.5 mole of ethanol, C2H5OH.

Thinking process:This question is assessing Chemical Calculation.Since the question states complete combustion, please note that the

only two products formed are carbon dioxide and water.

You will need to write out the balanced chemical equations for the above:Option A: C + O2 CO2Option B: C3H8 + 5O2 3CO2 + 4H2OOption C: C2H4 + 3O2 2CO2 + 2H2OOption D: C2H5OH + 3O2 2CO2 + 3H2O

** This question can be challenging as you will need to be able to writebalanced chemical equation to represent the combustion process.

47 Small portions of aqueous potassium iodide and of acidified aqueouspotassium manganate(VII) were added separately to each of the foursolutions. The colour changes seen are shown in the table.

Solutions Potassium iodide Potassium manganate(VII)1234

Colourless to brownColourless to brownNo visible changeNo visible change

Purple to colourlessNo visible changePurple to colourlessNo visible change


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On the other hand, KMnO4 being an oxidising agent, will oxidise othersand itself is reduced, as observed by the change in colour from purpleto colourless.

Since you are required to choose solutions which can act as oxidizingagents, the solutions must be able to oxidise KI.

Which solutions can act as an oxidizing agent?

A 1 only B 1 and 2 onlyC 1 and 3 only D 2 and 4 only.

48 Carbon dioxide is produced from the burning of carbon monoxide inoxygen according to the reaction.

2CO (g) + O2 (g) 2CO2 (g)

20 cm3 of carbon monoxide was reacted with 15 cm3 of oxygen at room

condition. What is the total volume of gases measured at the end of thereaction?

A 0 cm3B 10 cm3C 25 cm3D 35 cm3

Thinking process:This question is assessing Chemical Calculation. Since the reactants andproducts are all in gaseous states, you can compare the mole ratio todetermine the volume of gases. However, please note that you are required toidentify which gas is acting as the limiting reagent here.

To determine the limiting reagent, you have to compare the mole ratio of thereactant to the product.

Based on the chemical equation above, you will observe that mole ratio ofCO : O2 is 2 : 1. Thus when 20 cm

3 of CO will require 10 cm3 of O2 in thereaction. However, the volume of O2 present is 15 cm

3. Hence, there will be5 cm3 of O2 unreacted. From this, we know that O2 is in excess while CO is thelimiting reagent.

To determine the volume of CO produced we use the mole ratio (as shown)


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49 The table below refers to four metals and some of their compounds.

Metal Action of dilutesulfuric acid onmetal

Effect ofhydrogen onheated oxide

Action of metal onsolution of thesulfate of S

P Hydrogen evolved Reduced No reactionQ No reaction Reduced No reactionR Hydrogen evolved No action S formedS Hydrogen evolved No action No reaction

Which one of the following is the order of the reactivity?

Most reactive Least ReactiveA Q P S RB R P S QC R S P QD R Q P S

Thinking process:

This question is assessing you on your understanding of the Reactivity Seriesof Metals. From the table it is observed that Q is the least reactive as it doesnot react with acid and also it is unable to displace the other metals from theirmetal salt solutions. Hence options A and B are out.Metal R is the most reactive as it reacts with acid and is able to displace S fromits salt solution. This means that R is more reactive than S.


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50 Several tests were conducted for a colourless solution S to determine itschemical properties and the observations were recorded below.

Which ions could be present in S?

A Calcium and nitrateB Potassium and nitrateC Sodium and bromideD Sodium and ammonium

Thinking process:This question is assessing the topic Qualitative Analysis.Test 1 is a cation test. However, there is no ppt observed. So it cannot becalcium, as stated in Option A.

Besides serving as a cation test, it is also required in the test for nitrate, wherebesides addition of aqueous NaOH, aluminium powder is also added and themixture is warmed. The test for nitrate is positive as a pungent gas, which is

ammonia, is produced. This is further confirmed as the ammonia gas whenbubbled in aqueous iron(III) chloride will produce brown ppt, as ammonia gaswould have dissolved in water to form aqueous ammonia and reacts with thecation, Fe3+.

Test Observations

1. To a portion of S, addexcess aqueous sodiumhydroxide

No visible observation

2. Add aluminium powder toTest 1. Warm mixture gently.

Effervescence of pungent gas whichgave brown precipitate when bubbledinto aqueous iron (III) chloride


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Answer Sheet for MCQ

1D

16A

31D

46D

2B

17D

32A

47B

3B

18B

33B

48C

4D

19D

34A

49C

5 B 20 B 35 D 50 B

6B

21B

36A

7B

22A

37B

8C

23C

38B

9D

24C

39C

10C

25D

40B

** Please change the question numbers No. 25 to 24 and No. 24 to No. 25.

11C

26B

41C

12A

27A

42B

13C

28D

43A

14B

29B

44B

15A

30D

45B


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GroupI II III IV V VI VII 0

1

HHydrogen

1

4

HeHelium

2

7

LiLithium

3

9

BeBeryllium

4

11

BBoron

5

12

CCarbon

6

14

NNitrogen

7

16

OOxygen

8

19

FFluorine

9

20

NeNeon

10

23

NaSodium

11

24

MgMagnesium

12

27

AlAluminium

13

28

SiSilicon

14

31

PPhosphorus

15

32

SSulfur

16

35.5

ClChlorine

17

40

ArArgon

18

39

KPotassium

19

40

CaCalcium

20

45

ScScandium

21

48

TiTitanium

22

51

VVanadium

23

52

CrChromium

24

55

MnManganese

25

56

FeIron

26

59

CoCobalt

27

59

NiNickel

28

64

CuCopper

29

65

ZnZinc

30

70

GaGallium

31

73

GeGermanium

32

75

AsArsenic

33

79

SeSelenium

34

80

BrBromine

35

84

KrKrypton

36

85

RbRubidium

37

88

SrStrontium

38

89

YYttrium

39

91

ZrZirconium

40

93

NbNiobium

41

96

MoMolybdenum

42

TcTechnetium

43

101

RuRuthenium

44

103

RhRhodium

45

106

PdPalladium

46

108

AgSilver

47

112

CdCadmium

48

115

InIndium

49

119

SnTin

50

122

SbAntimony

51

128

TeTellurium

52

127

IIodine

53

131

XeXenon

54133

CsCaesium

55

137

BaBarium

56

139

LaLanthanum

57 *

178

HfHafnium

72

181

TaTantalum

73

184

WTungsten

74

186

ReRhenium

75

190

OsOsmium

76

192

IrIridium

77

195

PtPlatinum

78

197

AuGold

79

201

HgMercury

80

204

TlThallium

81

207

PbLead

82

209

BiBismuth

83

PoPolonium

84

AtAstatine

85

RnRadon

86

FrFrancium

87

226

RaRadium

88

227

AcActinium

89

*58-71 Lanthanoid series

90-103Actinoid series140

CeCerium

58

141

PrPraseodymium

59

144

NdNeodymium

60

PmPromethium

61

150

SmSamarium

62

152

EuEuropium

63

157

GdGadolinium

64

159

TbTerbium

65

162

DyDysprosium

66

165

HoHolmium

67

167

ErErbium

68

169

TmThulium

69

173

YbYtterbium

70

175

LuLutetium

71

Key

a

Xb

a = relative atomic mass

X = atomic symbol

b=proton(atomic)number

232

ThThorium

90

PaProtactinium

91

238

UUranium

92

NpNeptunium

93

PuPlutonium

94

AmAmericium

95

CmCurium

96

BkBerkelium

97

CfCalifornium

98

EsEinsteinium

99

FmFermium

100

MdMendelevium

101

NoNobelium

102

LrLawrencium

103


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Sci(Chem)MCQ (Caa30 Apr 2012) With Answers