Methyl acetate is hydrolyzed by add to form acetic acid and methanol. A solution

Question

Methyl acetate is hydrolyzed by add to form acetic acid and methanol. A solution of methyl acetate is hydrolyzed in the presence of 1M HCl at 25 degree C. Aliquots of equal volumes are removed at given times and titrated with a solution of NaOH to neutralize the acid. Thus, the amount of NaOH added to neutralize the acid is a reflection of the total concentration of add in the system. How would you use the volume of NaOH to calculate a value that is proportional to the concentration of Methyl acetate? Note, methyl acetate is hydrolyzed by HCl in a 1:1 stoichiometry and HCl is neutralized by NaOH with a 1:1 stoichiometry. Calculate the first-order rate constant from the experimental data in the table.

Explanation / Answer

4. Hydrolysis of methyl acetate with HCl

1 mole of HCl would hydrolyse 1 mole of methyl acetate to form 1 mole of acetic acid

1 mole of acetic acid reacts with 1 mole of NaOH

So,

moles of NaOH added = moles of acetic acid present in solution at that time.

moles of NaOH = molarity of NaOH x volume of NaOH used for titration

Now,

we have, initial moles of methyl acetate in solution

So,

moles of methyl acetate present say at time t = total moles of methyl acetate - moles of NaOH used

plotting amount of ln(methyl acetate left in solution after time t) versus time will give us straight line, with slope = -k

k = rate constant for first-order reaction

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