KINETICS OF THE ACID CATALYSED HYDROLYSIS OF METHYL ACETATE Background knowledge The acid catalysed hydrolysis of methyl

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KINETICS OF THE ACID CATALYSED HYDROLYSIS OF METHYL ACETATE
Background knowledge
The acid catalysed hydrolysis of methyl acetate 𝐻𝐻3𝑂𝑂+
𝐶𝐶𝐻𝐻 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐻𝐻 +𝐻𝐻 𝐶𝐶 �⎯⎯� 𝐶𝐶𝐻𝐻 𝐶𝐶𝐶𝐶𝐶𝐶𝐻𝐻+𝐶𝐶𝐻𝐻 𝐶𝐶𝐻𝐻 (1)
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methyl acetate acetic acid methanol (an ester) (an acid) (an
alcohol)
given by
= k’[CH3COOCH3][H2O]
Since water is also the solvent for the reaction, it is present
in a large excess. If the ester concentration were initially 1 mol
L-1 and then reduced to 0.5 mol L-1, its concentration would change
by 50%. The concentration of water present would change by less
than 1% in the same time, and therefore remains effectively
constant. Thus the equation becomes
is an example of a catalysed second order reaction whose rate at
constant H3O+ concentrations is
𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 = ∆[𝐶𝐶𝐻𝐻3𝐶𝐶𝑂𝑂𝑂𝑂𝐶𝐶𝐻𝐻3] = ∆[𝐶𝐶𝐻𝐻3𝐶𝐶𝑂𝑂𝑂𝑂𝐻𝐻] (2) ∆𝑡𝑡
∆𝑡𝑡
Rate = k[CH3COOCH3] (3) This is an example of a pseudo first
order reaction.
This essentially means that the rate of the reaction will be
directly related to any change in concentration of methyl acetate
(first order) because the concentration of water in this reaction
is so large it remains effectively constant.
As shown by Equation 2 the progress of the reaction may be
monitored either by the decrease in ester concentration with time
or by the increase in acetic acid concentration with time. The
latter is monitored in this experiment, by titration with
standardised base. This is done by removal of aliquots from
reaction flasks at regular times during the reaction and
drastically slowing any further reaction in them by cooling to ice
temperature, followed by titration.
Questions
Graph 2- Room temperature
1 .clear and descriptive title
2 • labelled and marked axes with units
3 • axes range appropriate
4 • correct line of best fit
5 • outliers either identified in table and not
plotted, or plotted but identified and not included in
lob

Kinetics Of The Acid Catalysed Hydrolysis Of Methyl Acetate Background Knowledge The Acid Catalysed Hydrolysis Of Methyl 1 (83.35 KiB) Viewed 25 times

Table 2: Experimental data for the hydrolysis of methyl acetate at room temperature. Room temperature rate constant, k₂: 22°C = 295.15K Time Initial burette Final burette Vt(mL) Voo - Vt (min:sec) reading (mL) reading (mL) 1:40 0.00 26.80 26.80 40.10-26.80= 15:55 0.00 29.20 29.20 40.10-29.20= 21:16 0.00 31.00 31.00 40.10-31.00= 31:00 0.00 31.00 31.00 40.10-31.00= 40:00 0.00 31.20 31.20 40.10-31.20= 50:50 0.00 31.40 31.40 40.10-31.40= In(V∞ - Vt) 13.30 10.90 9.10 9.10 8.90 8.70
60:00 ∞ 0.00 0.00 Calculations 32.50 40.10 32.50 40.10 40.10-32.50= 7.60 0
k2 = 22 °C (room temperature)
Using the Arrhenius equation K2 K1 In- 1 1 a - RT₂ T1