UNIVERSITI TEKNOLOGI MARA

FAKULTI KEJURUTERAAN KIMIA

ENGINEERING CHEMISTRY LABORATORY

(CHE485)

NO Title Allocated Marks (%) Marks1 Abstract/Summary 52 Introduction 53 Aims 54 Theory 55 Apparatus 56 Methodology/Procedure 107 Results 108 Calculations 109 Discussion 2010 Conclusion 1011 Recommendations 512 Reference 513 Appendix 5

TOTAL MARKS 100

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NAME : STUDENT NO :GROUP : EXPERIMENT : 1 – DETERMINATION OF THE CONCENTRATION OF ACETIC ACID IN VINEGARDATE PERFORMED : SEMESTER : 1PROGRAMME / CODE : SUBMIT TO :

1.1 SUMMARY

The main point of this experiment is to determine the concentration of acetic acid in

vinegar. By performing titration process the concentration of acetic acid in vinegar can be

determined by calculating both molarity and percent by mass of acetic acid in vinegar itself.

There are two parts in this experiment, which are standardization of sodium hydroxide

solution and determining the molarity of acetic acid and mass percent in vinegar. In the first

part which is the standardization of sodium hydroxide solution, NaOH as the titrant is added

carefully into the KHP solution and the pH is recorded with 1 ml additions of NaOH. The

graph of pH versus NaOH is plotted and from the equivalent point, the molarity of acetic acid

is calculated. These steps were repeated twice. In part two, which is determination of the

molarity of acetid acid and mass percent in vinegar, acetic acid is titrated with NaOH solution

and pH is recorded with 1 ml additions of NaOH. From the equivalent point, the volume of

NaOH that required to neutralize the vinegar in each titration is determined. Hence, by

undergoes a few steps of calculation, the percent by mass of acetic acid is calculated.

1.2 INTRODUCTION

Vinegar is a dilute solution of acetic acid. Its molecular formula is CH3COOH. The

molarity and percent by mass of acetic acid in vinegar, can be determined by performing

titration process which the data is represented via graph of titration curve. Titration process is

a volumetric technique where a solution of known concentration is added to the second

reactant of unkown concentration until the equivalent point is reached. The equivalence point

is the point when the titrant has been added in exactly the right quantity to react

stoichiometrically with the another reactant. Equivalent point occurs when the moles of acid

in the solution equals the moles of base added in the titration. Once the equivalent point is

reached, the volume of based that is required to completely neutralize the the acid can be

determined from the graph at the equivalent point. Hence molarity and percent by mass of

acetic acid in the vinegar solution can be calculated.

Concentration of solution is the amount of solute in a given amount of solvent. While

dilute solutions contain small amount of solute in a given amount of solvent. The molarity and

percent by mass of acetic acid in vinegar can be determined through titration process.There

are two formulas to express the concentration :

Molarity is the number of moles of solute per liter of solution;

Molarity(M) = moles of soluteliter of solution

Percent by mass is the mass in grams of solute per 100 grams of solution ;

Percent solute = gramsof solutegrams of solution

x 100%

1.3 AIMS

The aim of the experiment is to determine the concentration of acetic acid in vinegar by

calculating both molarity and percent by mass of acetic acid by performing titration process.

1.4 THEORY

Titration is a volumetric analysis, which adding a measured amount of known

concentration into another solution of unknown concentration from a graduated vessel called

burette and the substance to be determined is said to be titrated. The process must proceed

stoichiometrically. The type of chemical reaction occurring between the two solutions is

called a neutralization reaction, which the titrant is a base and the titrated solution is an acid.

Equivalent point is a stage which shows the completion of reaction between both

known and unknown concentration of the solution when the amount of added reagent is

exactly and stoichiometrically equivalent to the solution in the titrated solution. Once the

reaction has reached equivalent point, there is a sudden change in pH. pH in an aqueous

solution is related to its hydrogen concentration. In hydrogen ion concentration, pH is defined

as negative logarithm.

pH= -log[H3O+]

pH is the method of expressing the acidity or basicity if a solution. Solutions with pH<7 are

acidic, pH=7 are neutral and pH>7 are basic. As sodium hydroxide is added to the acid

solution, some of the hydrogen ions will be neutralized. As the hydrogen ion concentration

decreases, the pH of the solution will gradually increases. When sufficient NaOH is added to

completely neutralize the acid, the next drop of NaOH added will cause a sudden sharp

increase in pH. In this experiment, potassium hydrogen phthalate (KHP) is titrated with

NaOH solution. The reaction equation for this is :

KHC8H4O4(aq) + NaOH(aq) KNaC8H4O4(aq) + H2O (l)

Once the sodium hydroxide has been stanbdardized it then titrated with 10.00ml of

vinegar. The reaction equation for vinegar with NaOH is :

CH3COOH(aq) + NaOH(aq) NaCH3COO(aq) + H20(l)

In second part of this experiment, titration of a vinegar sample with a standardized

sodium hydroxide solution is performed. A primary standard acid solution is initially prepared

to standardize the sodium hydroxide solution. By dissolving a weighed quantity of pure acid

or base in a known volume of solution. Primary standard acid or bases have several common

characteristics :

They must be available in at least 99.9 purity

They must have a high molar mass to minimize error in weighing

They must be stable upon heating

They must be soluble in the solvent of interest

Potassium hydrogen phthalate, KHC8H4O4, and oxalic acid, (COOH)2, are common primary

standard acids. Sodium carbonate, Na2CO3, is the most commonly used base. Most acids and

bases are mostly available in primary standard form. Titration of the solution with a primary

standard should be performed to standardize one of these acidic or basic solutions.

1.5 APPARATUS

Weighing balance

250 ml beaker

Glass rod

pH meter

burette

retort stand with clamp

10mL volumetric pipette

Erlenmeyer flask

filter funnel

magnetic stirrer

MATERIALS

Distilled water

3.04g of KHP solid

6.00g of NaOH solid

10.00ml of acetic acid

1.6 PROCEDURE

PART A : Standardization of sodium hydroxide solution

1. 250 mL of 0.6M sodium hydroxide solution is prepared in a beaker from NaOH solid.

The amount of NaOH solid required is calculated.

2. A beaker is placed on the balance and is tared. 1.5 grams of KHP is added to the

beaker and the reading is only recorded approximately to the nearest 0.0015g. KHP

solution is prepared with 30mL of distilled water in a beaker.

3. Next, KHP solution is titrated with NaOH solution using a graduated vessel, burette

and the pH is recorded for every additions of 1mL NaOH solution.

4. The steps are repeated twice. Another solution for NaOH standardization is prepared.

5. The graph of pH versus NaOH is plotted and the equivalence point is determined. The

volume of NaOH required to neutralize the KHP solution in each titration is

calculated.

6. The molarity of sodium hydroxide for both titration is calculated.

7. Finally, the average molarity of the sodium hydroxide solution is also calculated.

PART B : Molarity of acetic acid and mass percent in vinegar

1. 10.00 mL of acetic acid is measured in the 10mL volumetric acid and is transferred to

250ml beaker. 85ml of distilled water is added to the beaker containing 10.00ml of

acetic acid to cover the pH electrode tip during the titration.

2. 1 ml of NaOH is added to the vinegar solution and the pH is recorded with 1 ml

additions of NaOH solution.

3. Next, the graph of pH versus NaOH volume added is plotted. From the plots, the

equivalence point is determined and the volume of NaOH solution required to

neutralize the vinegar in each titration is calculated and recorded in the table.

4. The steps are repeated twice.

5. The molarity of acetic acid in vinegar is calculated for both titrations.

6. The average molarity of acetic acid for each titration is also calculated.

7. Then, the percent by mass of acetic acid in vinegar solution for titrations 1 and 2 is

calculated.

8. Finally, the percent by mass of acetic acid in vinegar is calculated and recorded in the

table provided.

1.7 RESULTS & CALCULATION

PART A : Standardization of sodium hydroxide solution.

Titration 1 Titration 2

Mass of KHP (g) 1.504 1.500

Volume of NaOH solution to

neutralize the KHP solution (mL) 12.400 12.800

PART A

KHC8H4O4 (aq) + NaOH (aq) KNaC8H4O4 (aq) + H2O (l)

Titration 1

1) Moles of KHP used in the titration1 ;

massmolar mass

= 1.504 g204.2

= 0.007365 mol

2) Moles of NaOH required to neutralizing the moles of KHP ;

0.007365 mol KHP = 0.007365 mol NaOH

3) Molarity of the of NaOH solution ;

12.40 ml NaOH x 1 L

1000ml = 0.0124 L

Molarity = molvolume

= 0.007365mol

0.0124 L = 0.5939 M NaOH

Titration 2

4) Moles of KHP used in the titration 2 :

massmolar mass

= 1.500g204.2

= 0.007346 mol

5) Moles of NaOH required to neutralizing the moles of KHP ;

0.007346 mol KHP = 0.007346 mol NaOH

6) 12.80 ml NaOH x 1 L

1000ml = 0.0128 L

Molarity = molvolume

= 0.007346mol

0.0128 L = 0.5739 M NaOH

7) Average molarity of NaOH solution :

M 1+M 22

+ 0.5939+0.5739

2 = 0.5839 M of NaOH

PART B

Titration 1 Titration 2

Volume of NaOH to

neutralize the vinegar

solution (ml)

19.20 18.90

Titration 1

1) Moles of NaOH that reacted ;

19.20 ml NaOH x 1 L

1000ml = 0.01920 L NaOH

0.01920L NaOH x 0.600mol NaOHILNaOH solution

= 0.01920 mol

2) Moles of acetic acid neutralized by the moles of NaOH ;

0.01920 mol NaOH x 1molCH 3COOH

1mol NaOH = 0.01920 mol

3) The molarity of the CH3COOH solution ;

10ml CH3COOH x 1 L

1000ml = 0.010 L CH3COOH solution

M = molCH 3COOHLof solution

= 0.01920molCH 3COOH

0.01 Lsolution = 1.152M CH3COOH

4) Mass of acetic acid in the solution ;

10ml CH3COOH x 1 L

1000ml = 0.010l CH3COOH solution

0.01 L CH3C00H x 1.152molCH 3COOH

1L solution x60.06gCH 3COOH

1molCH 3COOH = 0.6919g

5) Mass of the acetic acid solution ;

10 ml CH3COOH x 1 gCH 3COOH solution1mlCH 3COOH solution

= 10.00g CH3COOH solution

6) Percent by mass of acetic acid in the solution

percent mass CH3COOH = 0.6919gCH 3COOH10.00gCH 3COOH

x 100% = 6.919 % CH3COOH

Titration 2

1) Moles of NaOH that reacted ;

18.90 ml NaOH x 1 L

1000ml = 0.01890 L NaOH

0.01840L NaOH x 0.600mol NaOHILNaOH solution

= 0.01134 mol

2) Moles of acetic acid neutralized by the moles of NaOH ;

0.01134 mol NaOH x 1molCH 3COOH

1mol NaOH = 0.01134mol

3) The molarity of the CH3COOH solution ;

10ml CH3COOH x 1 L

1000ml = 0.010 L CH3COOH solution

M = molCH 3COOHLof solution

= 0.01134molCH 3COOH

0.01 Lsolution = 1.134 M CH3COOH

4) Mass of acetic acid in the solution ;

10ml CH3COOH x 1 L

1000ml = 0.010l CH3COOH solution

0.10 L CH3C00H x 1.134molCH 3COOH

1 Lsolution x60.06gCH 3COOH

1molCH 3COOH = 0.6800g

5) Mass of the acetic acid solution ;

10 ml CH3COOH x 1 gCH 3COOH solution1mlCH 3COOH solution

= 10.00g CH3COOH solution

6) Percent by mass of acetic acid in the solution

percent mass CH3COOH = 0.6800gCH 3COOH10.00gCH 3COOH

x 100% = 6.800 % CH3COOH

7) Average percent by mass of acetic acid in the solution

T 1+T 22

= 6.919+6.8002

= 6.86%

1.8 DISCUSSION

In this experiment, titration is the measurement of the amount of a solution of known

concentration that required to react completely with a measured amount of a solution of

unknown concentration. Equivalent point is the point where a stoichiometrically equivalent

amount of base has been added to the acid.

When a stoichiometrically equivalent amount of base is added to a solution of acid,

which in this experiment the sample is NaOH and KHP solution, all the H+¿¿ ions present in

KHP react with an equivalent amount of OH−¿¿ ions from NaOH. The higher the mass of acid

prepared, the higher the volume of base added to neutralize. The reaction of H+¿¿ and OH−¿¿

ions produces this equation :

H+¿¿(aq) + OH−¿¿(aq) H2O (l)

Standardize means to determine a precise and accurate concentration, and the burette

is used to make accurate volume concentration of our NaOH solution. During the titration, we

added 1 ml of NaOH solution, drop by drop. Each drop, the ph reading is recorded and the

adding of 1ml of NaOH is continuosly till there is a sharp increase of ph reading. Then, we

continue by adding 0.5ml of NaOH, each drop till the ph reading is constant. The data is

expressed in the graph of titration curve. Besides, we have immersed the ph electrode during

the titration to cover the liquid junction during all measurement.

However, there is still have a few limitations in this kind of experiment. First, when

we weighing the powder of KHP, there were some fluctuations with the mass of the powder

which could not be prevented as there were many factors that could have affected it. Besides,

it was found that when pouring the diluted alkali solution, NaOH into the volumetric flask,

some residue of NaOH was left. This was washed with distilled water into flask but as soon as

the flask reached the meniscus line, no more could have been poured in, thus leaving some

residue in the beaker. Besides, when filling the burette with NaOH solution, we have made

certain that all air bubbles have been flushed from the tip before taking the initial volume

reading, check for the bubbles and full tip. This would have had an effect on the accuracy,

validity, and reliability of the results.

1.9 CONCLUSION

The molarity and percent by mass of acetic acid in vinegar can be determined by performing

titration process with a standardized sodium hydroxide solution. The molarity of acetic acid

and percent by mass of acetic acid in vinegar are 0.5839M and 6.86%.

2.0 RECOMMENDATIONS

First and foremost, I suggest we should wear approved safety goggles while working

in the lab. These safety goggles can protect our eyes from any hazardous materials or

anything. Besides, contact lens also should not be worn because during the experiment lab,

various fumes may accumulate under the lens and cause serious injuries or might be

blindness. Beside that, lab coat with the long hand is should be the most compulsory and we

should wear gloves when using any hazardous or toxic agent.

2.1 REFERENCES

1) Anne. (n.d.). Neutralising A Base With An Acid. Retrieved from

http://www.chemistryabout.com

2) Farlex. (n.d.). The Free Dictionary. Retrieved from

http://www.thefreedictionary.com/titration

3) Ucdavis. (n.d.).Titration. Retrieved from http://www.chemwiki.ucdavis.edu.

4) W.H.Freeman.(1995).Quantitative Analysis. Retrieved from http://www.ion.chem.usu.edu.

5) Brian.(2000).Titration. Retrieved from http://www.files.chem.vt.edu