The following statements predict the temperature dependence on the rate of reaction:
(A) Increase in temperature increases the rate of reaction.
(B) Increase in temperature decreases the rate of reaction.
(C) Increase in temperature by 10 °C doubles the reaction rate.
(D) An increase in temperature by 10 °C triples the rate of reaction.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A) and (C) only
Most reactions become faster on heating. A rise in temperature increases the kinetic energy of the molecules, so a larger fraction of collisions has energy equal to or above the activation energy. This is expressed by the Arrhenius equation:
\( \displaystyle k = A\,e^{-E_a/RT} \)
As T increases, \( E_a/RT \) becomes smaller and k becomes larger. For a typical reaction near room temperature, a rise of 10° nearly doubles the rate constant.
(A) Increase in temperature increases the rate of reaction. — Correct. More molecules cross the energy barrier, so k and the rate increase.
(B) Increase in temperature decreases the rate of reaction. — Incorrect. It is the reverse of (A); heating lowers \( E_a/RT \) and raises k.
(C) Increase in temperature by 10 °C doubles the reaction rate. — Correct. This is the usual rule: the rate constant is nearly doubled for a 10° rise (temperature coefficient about 2).
(D) An increase in temperature by 10 °C triples the rate of reaction. — Incorrect. The general rule is about doubling; (C) and (D) cannot both hold.
NCERT (2026-27 edition):
Temperature Dependence of the Rate of a Reaction
