CBSE Class 12 Chemistry 2023: question 20

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Step-by-step solution

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1. **Rate constant $k$ increases** with rise in temperature.

   ½ mark

2. Justification: by the Arrhenius equation $k=A{e}^{-E_a/RT}$, increasing $T$ makes $-E_a/RT$ less negative, so $k$ increases; more molecules acquire energy ≥ $E_a$, so the rate (and $k$) rises.

   ½ mark

3. **Activation energy $E_a$ remains unchanged** (no effect of temperature).

   ½ mark

4. Justification: $E_a$ is the energy difference between the activated complex and the reactants; it depends only on the nature of the reactants (and catalyst), not on temperature.

   ½ mark

Answer: $k$ increases; $E_a$ remains unchanged

Revise the chapter

• Chapter: Chemical Kinetics (notes, formulas, where marks are lost and every past question)
• Topic: Arrhenius Equation and Activation Energy