Question

Which of the following is an example of pseudo unimolecular reaction?

• A. $CH _{3} COOCH _{3}+ H _{2} O \stackrel{ H ^{+}}{\longrightarrow} CH _{3} COOH ^{+} CH _{3} OH$
• B. $CH _{3} COOCH _{3}{ }^{+} H _{2} O \stackrel{ OH ^{-}}{\longrightarrow} CH _{3} COOH ^{+} CH _{3} OH$
• C. $2 FeCl _{3}+ SnCl _{2} \rightarrow SnCl _{4}+2 FeCl _{2}$
• D. $NaOH + HCl \rightarrow NaCl + H _{2} O$

Answer 1

Answer: (A)

When in any chemical reaction, one of the reactant is present in large excess, then the secondorder reaction becomes first-order reaction and is known as pseudo unimolecular reaction e.g.,
$CH _{3} COOCH _{3}^{+} H _{2} O \xrightarrow{H^{+}} CH _{3} COOH ^{+} CH _{3} OH$
in this reaction molecularity is 2 but order of reaction is found to be first order experimentally, so it is an example of pseudo unimolecular reaction.