Question

The hydrolysis of ethyl acetate,
$CH_{3}COOC_{2}H_{5}+H_{2}O $ $\ce{ ->[H^{+}] }$ $CH_{3}COOH+C_{2}H_{5}OH$ is a reaction of

• A. zero order
• B. pseudo first order
• C. second order
• D. third order.

Answer 1

Answer: (B)

A reaction which is not the first-order reaction naturally but made the first order by increasing or decreasing the concentration of one or the other reactant is known as Pseudo first-order reaction.
Hydrolysis of ethyl acetate in presence of an excess of water:
$CH _{3} COOC _{2} H _{5}+ H _{2} O$ (excess) $\ce{->[H +]} CH _{3} COOH + C _{2} H _{5} OH$
$r = k \left[ CH _{3} COOC _{2} H _{5}\right]^{2}\left[ H _{2} O \right]^{0}$
Excess $\left[ H _{2} O \right]$ can cause the independency of reaction on $H _{2} O$.
Hence, it is a pseudo-first-order reaction.