Arrange the following in the increasing order of rate of the second order reaction
Reactants → products
(A) Reaction at 298 K
(B) Reaction at 298 K with catalyst
(C) Reaction at 500 K with catalyst and double the initial concentration of reactant
(D) Reaction at 500 K with double the initial concentration of reactant
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (B), (D), (C)
For a second-order reaction:
$\text{Rate} \propto k[A]^2$
where
- k increases with temperature (Arrhenius equation)
- Catalyst increases k
- Doubling concentration increases rate by $2^2 = 4$ times
-
(When concentration doubles in a second-order reaction, the rate increases four times because the concentration term is squared in the rate law. So doubling concentration gives: 2² = 4 times increase in rate.)
- (A): 298 K, no catalyst → slowest
- (B): 298 K + catalyst → faster than (A)
- (D): 500 K + double concentration → much faster (higher k and 4× concentration effect)
- (C): 500 K + catalyst + double concentration → fastest
Increasing order of rate: (A) < (B) < (D) < (C)