Question

Which of the following is an example of pseudo first order reaction?

• A. Thermal decomposition of \(N_2O_5\) gas
• B. Decomposition of HI on gold surface
• C. Decomposition of \(NH_3\) on platinum surface
• D. Inversion of sucrose
• E. Hydrogenation of ethene

Hint:

Remember, in pseudo first order reactions, one or more reactants are present in such excess that they effectively remain constant throughout the reaction.

Answer 1

The Correct Option is D

Step 1: A pseudo first order reaction appears to be first order because one reactant is in such excess that its concentration does not noticeably change during the reaction. 
Step 2: In the inversion of sucrose, sucrose is hydrolyzed to glucose and fructose in the presence of acid. The reaction is first order with respect to sucrose, with the acid effectively being in excess. 
Step 3: This makes it a pseudo first order reaction as the concentration of water and acid do not limit the reaction rate. 
Step 4: Therefore, the correct answer is the inversion of sucrose.