CHM256 EXP 3 Laboratory Manual analytic chm PDF

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ANALYTICAL CHEMISTRYREPORT SHEETExperiment No 3Title ACID – BASED TITRATION II (BACKTITRATION)DETERMINATION THE PERCENT (W/W) OFTHE ACTIVE INGREDIENT IN ASPIRINTABLETName 1. Siti Aqilah Najwa Binti Mohd Jalil(2019292794)2. Alyaa Saffiah Binti Azahar (2019234724)Student ID 1. 20192927942. 2019234724C...

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ANALYTICAL CHEMISTRY

ANALYTICAL CHEMISTRY

REPORT SHEET Experiment No

3

Title

ACID – BASED TITRATION II (BACK TITRATION) DETERMINATION THE PERCENT (W/W) OF THE ACTIVE INGREDIENT IN ASPIRIN TABLET

Name

1. Siti Aqilah Najwa Binti Mohd Jalil (2019292794) 2. Alyaa Saffiah Binti Azahar (2019234724)

Student ID

1. 2019292794 2. 2019234724

Course

CHM256 (Analytical Chemistry)

Group

AS1204_6 (Group 7)

Date of Experiment

22 April 2021

Date of Submission

4 May 2021

Lecturer’s Name

Madam Umi Kalsum Abdul Karim

ANALYTICAL CHEMISTRY

EXPERIMENT 3 ACID – BASE TITRATION II (BACK TITRATION) 1. State the objective of the experiment. I.

II.

To determine the percent (w/w) of the active ingredient, acetylsalicylic acid (C9H8O4) in aspirin tablets. To learn to calculate molarity based on titrations

2. Describe the procedure (use schematic diagram if necessary). A. Standardization of HCl solution with Na2CO3

1. The procedure was followed as in Experiment 1 to standardize your HCl solution. The solution was titrated with the primary standard of Na2CO3. the data was recorded in Table2 Equation: Na2CO3 + 2HCl ฀ 2NaCl + H2O + CO2 B. Preparation of 1.0 M NaOH (Standardization of NaOH solution with HCl) 1. The burette was filled with NaOH solution. Pipette solution of HCl into 250 mL conical flask. 2 - 3 drops of phenolphthalein was dropped as indicator. 2. The HCl in the conical flask was titrated with the NaOH from the burette slowly while shaking the flask until the indicator color changed. 3. From titration and calculation in the lab, you prepare 1.0 M NaOH from HCl as a secondary standard solution.

C. Hydrolysis of aspirin 1. one commercial was collecting aspirin tablets. the brand name was recorded and % content (mass) of the active ingredient in the tablet was calculated. 2. The aspirin tablet was weighed accurately in a weighing paper and transferred into a 250 mL conical flask. 3. 25 mL (use pipette) of 1.0 M NaOH solution and 25 mL of water was added to the tablet. This mixture is heated until it boils for about 10 minutes in order to hydrolyze the aspirin. 4. The solution was cooled at room temperature then was transferred quantitatively into 250 mL volumetric flask. The solution was diluted to the mark carefully using a dropper when the level is close to the calibration mark.

ANALYTICAL CHEMISTRY

D. Back titration 1. 25 mL of aspirin solution was pipetted into a 250 mL conical flask. 2. 1-2 drops of phenol red or phenolphthalein was added as indicator 3. The aspirin solution was titrated in the 250 mL conical flask with the HCI solution prepared in (A) from the burette slowly while shaking the flask until the indicator changes color (phenol red: light red to light yellow; phenolphthalein: pink to colorless). Your reading at the end point of the titration was recorded . 4.The steps were repeated 2-3 times and all readings were recorded in Table 3. 5.The % w/w of acetylsalicylic was calculated in aspirin tablets.

RESULT/DATA ANALYSIS Table 1 Commercial/brand name of aspirin tablet

Millisprin

Name of manufacturer

KCK Pharmaceutical

Mass per tablet of active ingredient (acetylsalicylic acid) stated on the label

900 mg

Mass of aspirin tablet

1.1567 g

Calculated % w/w

77.81 %

Table 2 Standardization of HCl solution. Titration

Rough

1

2

3

Final burette reading

23.70

23.70

23.80

Initial burette reading

0.00

0.00

0.00

Volume of HCl used

23.70

23.70

23.80

a) Average volume of HCl: 23.73 mL b) Volume of Na 2CO3 used: 25.00 mL c) Molarity of Na2CO3: 0.05 M Standardization of NaOH solution with HCl Molarity of NaOH: 1.0 M

ANALYTICAL CHEMISTRY

Table 3 Titration of aspirin solution with HCl Titration

Rough

1

2

3

Final burette reading

13.90

13.10

13.10

Initial burette reading

0.00

0.00

0.00

Volume of HCl used

13.90

13.10

13.10

a) Average volume of HCl: 13.37 mL b) Initial volume of NaOH used to hydrolyze aspirin: 25.00 mL

ANALYTICAL CHEMISTRY

CALCULATIONS 1a) Based on the data obtained in Table 2 calculate the exact molarity of HCl. Use (MaVa / MbVb) = a/b Molarity = MaVa (HCl) = a MbVb (Na2CO3) b

Na2CO3 (aq) + 2 HCl (aq) → 2 NaCl (aq) + CO2 (g) + H2O (l) =

x M x 0.02373L = 2 0.05 M x 0.025 L 1 0.02373 x M/L = 0.00125 (2) M/L x M = 0.0025M/L 0.02373L = 0.105 M of Hydrochloric Acid

a) Using back titration method, calculate the % (w/w) ASA in the aspirin tablet. i) Calculate the initial mole of NaOH used for hydrolysis.

Initial mole of NaOH = M= n V 1.0 M=

n 0.025L

Number of mole of NaOH = 0.025mol ii) Based on Equation (2), calculate the mole of excess (unreacted) NaOH. (Remember in C: Hydrolysis of aspirin, solution mix with NaOH is diluted 10 x [25 mL into 250 mL]. Need to find mol NaOH before dilution) NaOH + HCl = NaCl + H2O

1 mole of NOH = 1 mole of HCl Mole of HCl =Molarity x volume (L) =0.105 M x 0.01337 L =0.001404 mole So, mole of excess NaOH = 0.001404 mole x 10x = 0.01404 mole of excess NaOH

ANALYTICAL CHEMISTRY

iii) Calculate the mole of NaOH that has actually reacted with acetylsalicylic acid.

Mole of NaOH reacted with acetylsalicylic acid = initial NaOH - Final NaOH = 0.025 mole - 0.014 mole =0.011 mole of NaOH that has actually reacted

iv) Based on Equation (1), calculate the mole of reacted acetylsalicylic acid (ASA) in the solution. CH3COO-C6H4-COOH + 2NaOH ฀ CH3COO- Na+ + HO-C6H4-COO- Na+

mole of reacted acetylsalicylic acid (ASA) = mole of NaOH x 1 mole of ASA 2 mole OF NaOH = 0.011 mole NaOH x 1 mole of ASA 2 mole OF NaOH = 0.055 mole of reacted acetylsalicylic acid

v) Calculate the mass then the % w/w of acetylsalicylic acid in the tablet. %w/w = weight of acetylsalicylic acid (g) weight of Aspirin (g) Weight / mass of acetylsalicylic acid (g) = ½ mole Of NaOH react x molar mass = 0.0055 mole x 180g/mol = 0.9909 g %w/w =

0.99 b. 1.1567 g

X 100

= 85.58 % vi) Compare the % w/w calculated in Table 1 and the result obtained in (v). Calculate the % error. (% Error = measured / calc value - true value/ standard x 100 ) True value / standard

(% Error = 85.58% - 77.81% x 100 ) 77.81% % Error = 9.99 %

ANALYTICAL CHEMISTRY

Conclusion: This experiment was conducted to determine the percent (w/w) of the active ingredient of acetylsalicylic acid (C9H8O4) in aspirin tablets. To find the average volume of HCl used in this experiment, the final burette reading will be subtracted with the initial burette. So the volume of HCl used is 23.27 mL. Hence, the exact molarity of HCl that we can obtain from this experiment is 0.105M. The calculations that we used are (MaVa / MbVb) = a/b. For the initial mole of NaOH solution used for the hydrolysis, we obtain 0.025 mole and for the excess mole of NaOH is 0.01404 mole. Thus we can get 0.011 mole of NaOH that has actually reacted with acetylsalicylic acid. From the mass of acetylsalicylic acid (g) that we obtain we can find the percentage error for this experiment. The error that we can obtain from this experiment is 9.99% when the mass of acetylsalicylic acid is 0.9909g. To sum up everything that has been stated so far, the objective of the experiment is fulfilled....