JEE Advanced 2016 · Paper 1 · Chemistry Q24

ChemistryMultiple correct+4 / -2Question 24 of 54

According to the Arrhenius equation,

a high activation energy usually implies a fast reaction.

rate constant increases with increase in temperature. This is due to a greater number of collisions whose energy exceeds the activation energy.

higher the magnitude of activation energy, stronger is the temperature dependence of the rate constant.

the pre-exponential factor is a measure of the rate at which collisions occur, irrespective of their energy.

Answer and worked solution

Official answer: B, C, D

Arrhenius equation: $k=Ae^{-E_a/RT}$ .

(A) A high $E_a$ makes $k$ small: a slow reaction. False.
(B) Raising $T$ increases the fraction of collisions with energy above $E_a$ , $e^{-E_a/RT}$ . True.
(C) $\dfrac{d\ln k}{dT}=\dfrac{E_a}{RT^2}$ , so a larger $E_a$ means stronger temperature dependence. True.
(D) $A$ reflects the collision frequency (with orientation), independent of energy. True.

(B), (C), (D)

Topics:Arrhenius equation Collision theory

JEE Advanced 2016 · Paper 1, Chemistry question 24