Chemical Kinetics questions will always be relevant, be it for AIIMS, NEET or JEE exam. These types of questions are based on an understanding of mathematical concepts like kinetics and rate of reaction. The first order reaction is common in all the three exams.
Chemical Kinetics Questions (Pseudo First Order Reaction)
1. Acid hydrolysis of esters such as CH3COOC2H5 in aqueous solution is an example of a pseudo first-order reaction.
2. The rate law for inversion of cane sugar is R=k [C12H22O11][H2O]. Find the concentration of sucrose if the rate of the reaction is 0.032 s-1 and rate constant k=0.005.
a) 5.8 M
b) 6 M
c) 6.2 M
d) 6.4 M
Answer: 6.4 M
3. What is the rate law of hydrolysis of CH3COOC2H5 in aqueous solution?
a) R=k [CH3COOC2H5]2
b) R=k [CH3COOC2H5]
c) R=k [CH3COOC2H5] [H2O]
d) R=kk’ [CH3COOC2H5][H2O]
Answer: R=k [CH3COOC2H5]
4. Which of the following is not true for a pseudo first-order reaction?
a) The reaction follows first order kinetics
b) Molecularity of the reaction should be one
c) The reactants such as water are present in excess and are assumed to be constant throughout the reaction
d) Unit of the rate constant is s-1
Answer: Molecularity of the reaction should be one
5. Which of the following is not similar between a first order and pseudo first order reaction?
a) The molecularity is one in both the reactions
b) Both follows first order kinetics
c) The unit of rate constant is s-1
d) The rate of the reaction depends only on one reactant
Answer: The molecularity is one in both the reactions
6. Which of the following is not an example of a pseudo first-order reaction?
a) CH3COOC2H5 + NaOH ? CH3COOH + H2O
b) CH3COOC2H5 + H2O ? CH3COOH + C2H5OH
c) C2H5COOC2H5 + H2O ? C2H5COOH + C2H5OH
d) C12H22O11 + H2O ? glucose + fructose
Answer: CH3COOC2H5 + NaOH ? CH3COOH + H2O
7. For the reaction C2H5COOC2H5 + H2O ? C2H5COOH + C2H5OH, find the concentration of [C2H5COOC2H5] if the rate constant k=0.2 and the rate of the reaction is 0.39 s-1.
a) 2.87 M
b) 2.01 M
c) 1.99 M
d) 1.95 M
Answer: 1.95 M
8. For a pseudo first-order reaction, what is the unit of the rate of the reaction?
b) mol L-1s-1
c) mol-1 L s-1
d) mol-2 L2 s-1
9. Reactions whose molecularity is one but order is more than one are known as pseudo first-order reactions.
10. Which of the following reactions is an example of a pseudo first-order reaction?
a) H2 + Br2 ? 2HBr
b) CH3CHO ? CH4 + CO
c) C12H22O11 + H2O ? glucose + fructose
d) PCl5 ? PCl3 + Cl2
Answer: C12H22O11 + H2O ? glucose + fructose