IA on aspirin hydrolysis in different HCI concentration (0.0625 -1M), measured using visible spectrophotometer.

1. Aspirin hydrolysis (Standard calibration plot)
Aspirin undergo hydrolysis to produce salicylic acid (SA) and acetic acid.
SA, active ingredient will react with Fe3+ to form violet product.
Standard calibration plot was done using SA.
Conc range from (1.56, 3.125, 6.25, 12.5, 25.0) in mg/100
1% FeCI3 solution was prepared.
Violet colorization monitored with colorimeter.
Fe3+ reacts with SA to produce
violet substance which can be measure with colorimeter
Procedure:
0.025g SA dissolve in 100ml water. (25mg/100).
HCI of diff conc (0.0625, 0.125, 0.25, 0.50, 1.00M) was prepared.
1ml SA added to cuvette.
1ml of acid of diff conc was added to cuvette containing 1ml of SA.
100ul of Fe3+ added and mix.
Abs was done at 565nm
Mechanism of aspirin hydrolysis to produce SA Aspirin 500mg was turn
into powder
Aspirin hydrolysis in diff HCI conc (0.0625 -1M), measured using visible spectrophotometer.

2. Go to expt – press calibrate Insert cuvette (violet sol), press collect
Insert a blank containing water
Press stop, and click on rainbow icon. Select abs vs conc. λ max at 565nm will
be automatically chosen
Type in concentration and press keep
Type in concentration and press keep
for 5 diff conc
Standard calibration plot is generated
Aspirin hydrolysis in diff HCI conc (0.0625 -1M), measured using visible spectrophotometer.

3. Hydrolysis of aspirin is very slow in acid (1M)
medium compared to water
y = 0.0945x + 0.016
R² = 0.9999
0
0.5
1
1.5
0 2 4 6 8 10 12 14
Abs
Conc SA/mg/100
Conc SA vs abs
Line best fit Abs = 0.0945 (Conc) + 0.016
1mol aspirin produces - 1mol SA
500mg aspirin contain 0.00277mol
0.00277mol aspirin produces 0.00277mol SA
RMM SA – 138.
0.00277mol x 138 = 382mg SA
Aspirin hydrolysis in diff HCI conc (0.0625 -1M), measured using visible spectrophotometer.
Conc
HCI/M
Abs Conc
SA/mg/100ml
water/o.0 0.449 4.58
0.0625 0.410 4.16
0.125 0.392 3.97
0.25 0.316 3.17
0.50 0.158 1.50
1.00 0.074 0.613
Abs = 0.0945 (Conc) + 0.016
0.449 = 0.0945 (Conc) + 0.016
Conc = 4.58mg/100
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 0.2 0.4 0.6 0.8 1 1.2
conc
SA/mg/100ml
conc HCI/M
conc HCI vs conc SA/mg/100ml
Hydrolysis of aspirin to SA decreases as conc of HCI increases
Might be due to Le Chatelier – equilibrium shifted to left due to presence
of acid, causing decrease in hydrolysis of aspirin in acidic medium.