IA on rate of hydrolysis of aspirin at different temperature, 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:
500mg aspirin dissolve in 100ml water.
1ml aspirin sol added to a tube placed at diff temp in water bath (30mins)
300ul of Fe3+ added and were mix together.
Abs was done at 565nm.
Process repeat at diff temp 26, 37, 45, 50, and 55C
Mechanism of aspirin hydrolysis to produce SA Aspirin 500mg was turn
into powder
Rate of Hydrolysis of aspirin at diff temp, 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
Rate of Hydrolysis of aspirin at diff temp, measured using visible spectrophotometer.

3. Rate of hydrolysis of aspirin over 30min
(Final conc SA – ini conc SA)/30min
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
Temp/
C
Ini abs Final
abs
Change in
conc
SA/mg/100
ml
Rate of
hydrolysis
26 0.680 0.710 0.3179 0.01059
37 0.730 1.209 5.069 0.1689
45 0.690 1.051 3.820 0.127
50 0.628 1.340 7.534 0.2511
55 0.645 1.950 13.8096 0.4603
Abs = 0.0945 (Conc) + 0.016
0.710 = 0.0945 (Conc) + 0.016
Conc = 7.343mg/100
Rate of hydrolysis seems to be increasing exponentially with temp
Rate of Hydrolysis of aspirin at diff temp, measured using visible spectrophotometer.
0
0.1
0.2
0.3
0.4
0.5
0.6
0 10 20 30 40 50 60
Rate
of
hydrolysis
temp/C
Temp vs Rate of hydrolysis