Lab Report - Determination Of Concentration Acetic Acid In Vinegar 2q4w25

UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN KIMIA ENGINEERING CHEMISTRY LABORATORY (CHE485) NAME STUDENT NO GROUP EXPERIMENT

: : : : 1 – DETERMINATION OF THE CONCENTRATION OF ACETIC ACID IN VINEGAR DATE PERFORMED : SEMESTER :1 PROGRAMME / CODE : SUBMIT TO :

NO 1 2 3 4 5 6 7 8 9 10 11 12 13

Title Abstract/Summary Introduction Aims Theory Apparatus Methodology/Procedure Results Calculations Discussion Conclusion Recommendations Reference Appendix TOTAL MARKS

Remarks : Checked by : -----------------------------Date :

Allocated Marks (%) 5 5 5 5 5 10 10 10 20 10 5 5 5 100

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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 solute liter of solution

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

grams of solute grams 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 4. 5. 6. 7.

neutralize the vinegar in each titration is calculated and recorded in the table. The steps are repeated twice. The molarity of acetic acid in vinegar is calculated for both titrations. The average molarity of acetic acid for each titration is also calculated. 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.

Mass of KHP (g) Volume of NaOH solution to neutralize the KHP solution (mL)

Titration 1 1.504

Titration 2 1.500

12.400

12.800

PART A KHC8H4O4 (aq) + NaOH (aq)

KNaC8H4O4 (aq) + H2O (l)

Titration 1 1) Moles of KHP used in the titration1 ; mass 1.504 g = molar mass 204.2 = 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 ; 1L 12.40 ml NaOH x 1000 ml = 0.0124 L Molarity =

mol volume

=

0.007365mol 0.0124 L

= 0.5939 M NaOH

Titration 2 4) Moles of KHP used in the titration 2 : mass 1.500 g = molar mass 204.2 = 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 Molarity =

1L 1000 ml

mol volume

=

= 0.0128 L

0.007346 mol 0.0128 L

= 0.5739 M NaOH

7) Average molarity of NaOH solution : M 1+ M 2 2

+

0.5939+ 0.5739 2

= 0.5839 M of NaOH

PART B Titration 1

Titration 2

19.20

18.90

Volume of NaOH to neutralize the vinegar solution (ml) Titration 1 1) Moles of NaOH that reacted ; 1L 19.20 ml NaOH x 1000 ml 0.01920L NaOH x

= 0.01920 L NaOH

0.600 mol NaOH IL NaOH solution

= 0.01920 mol

2) Moles of acetic acid neutralized by the moles of NaOH ; 1 mol CH 3 COOH 0.01920 mol NaOH x = 0.01920 mol 1 mol NaOH 3) The molarity of the CH3COOH solution ; 1L 10ml CH3COOH x 1000 ml = 0.010 L CH3COOH solution M=

mol CH 3 COOH L of solution

=

0.01920mol CH 3 COOH 0.01 L solution

= 1.152M CH3COOH

4) Mass of acetic acid in the solution ; 1L 10ml CH3COOH x 1000 ml = 0.010l CH3COOH solution

1.1 L CH3C00H x

1.152 mol CH 3 COOH 1 L solution

x

60.06 g CH 3 COOH 1 mol CH 3 COOH

=

0.6919g 5) Mass of the acetic acid solution ; 1 g CH 3 COOH solution 10 ml CH3COOH x 1 ml CH 3COOH solution

= 10.00g CH3COOH solution

6) Percent by mass of acetic acid in the solution 0.6919 g CH 3 COOH percent mass CH3COOH = 10.00 g CH 3 COOH

x 100% = 6.919 %

CH3COOH Titration 2 1) Moles of NaOH that reacted ; 1L 18.90 ml NaOH x 1000 ml = 0.01890 L NaOH 0.01840L NaOH x

0.600 mol NaOH IL NaOH solution

= 0.01134 mol

2) Moles of acetic acid neutralized by the moles of NaOH ; 1 mol CH 3 COOH 0.01134 mol NaOH x = 0.01134mol 1 mol NaOH 3) The molarity of the CH3COOH solution ; 1L 10ml CH3COOH x 1000 ml = 0.010 L CH3COOH solution M=

mol CH 3 COOH L of solution

=

0.01134 mol CH 3COOH 0.01 L solution

= 1.134 M CH3COOH

4) Mass of acetic acid in the solution ; 1L 10ml CH3COOH x 1000 ml = 0.010l CH3COOH solution 0.10 L CH3C00H x

1.134 mol CH 3 COOH 1 L solution

x

60.06 g CH 3 COOH 1 mol CH 3 COOH

=

0.6800g 5) Mass of the acetic acid solution ; 1 g CH 3 COOH solution 10 ml CH3COOH x 1 ml CH 3COOH solution

= 10.00g CH3COOH solution

6) Percent by mass of acetic acid in the solution 0.6800 g CH 3 COOH percent mass CH3COOH = 10.00 g CH 3 COOH

x 100% = 6.800 %

CH3COOH 7) Average percent by mass of acetic acid in the solution T 1+ T 2 6.919+ 6.800 = = 6.86% 2 2

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 −¿¿ KHP react with an equivalent amount of OH

+¿¿ H ions present in

ions from NaOH. The higher the mass of

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

+¿¿ H and

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, 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