What will happen when the temperature of a chemical reaction rises by 10 °C?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → rate constant is nearly doubled.
Most chemical reactions go faster at higher temperatures. It is found by experiment that for a rise in temperature of 10° the rate constant of a reaction becomes about two (sometimes up to three) times; the ratio is called the temperature coefficient:
\( \displaystyle \frac{k_{t+10}}{k_{t}} \approx 2 \)
The reason is given by the Arrhenius equation, \( k = A\,e^{-E_a/RT} \). Raising the temperature increases the fraction of molecules having energy equal to or greater than the activation energy, and for a 10° rise near room temperature this fraction is roughly doubled, so the rate constant is nearly doubled.
Why the other options are incorrect
Option (1) rate constant remains same. — Incorrect. k depends on temperature through \( e^{-E_a/RT} \); it stays constant only at a fixed temperature.
Option (3) rate constant decreases. — Incorrect. A higher temperature gives more molecules with enough energy to react, so k increases.
Option (4) rate constant increases by 10 times. — Incorrect. A 10° rise multiplies k by about 2 to 3, not 10.
NCERT (2026-27 edition):
Temperature Dependence of the Rate of a Reaction – …
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | 02-06 S2 29-05 S2 | – | – | – |