For a chemical reaction with a rise in temperature by 10°C, the rate constant becomes nearly
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 2 times
Based on the general principles of chemical kinetics, for a chemical reaction, a rise in temperature by 10°C usually results in the rate constant becoming nearly 2 times its original value.
Explanation: The Temperature Coefficient
The effect of temperature on the rate of a reaction is often expressed in terms of the temperature coefficient $(\eta)$, which is the ratio of the rate constants at two temperatures differing by 10°C.
- Rule of Thumb: For many common chemical reactions occurring near room temperature, the rate of reaction approximately doubles for every 10°C rise in temperature.
- Arrhenius Equation: This observation is grounded in the Arrhenius equation,
$k = Ae^{-E_a/RT}$
which shows that an increase in temperature increases the number of molecules with energy equal to or greater than the activation energy $(E_a)$.
Why the Rate Increases
While a 10°C rise only increases the average kinetic energy of molecules by about 3%, it significantly increases the fraction of "effective collisions". This is because a much larger number of molecules can now cross the energy barrier required for the reaction to proceed.