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A catalyst increases the rate of a chemical reaction by
Aproviding an alternative pathway with LOWER activation energy; $K_c$ is unchanged
Bincreasing the activation energy of the forward reaction
Cshifting the equilibrium toward products, increasing $K_c$
Dincreasing the kinetic energy of all reactant molecules
Answer & Solution
Correct answer: A. providing an alternative pathway with LOWER activation energy; $K_c$ is unchanged
1. NCERT §3.4 (Effect of Catalyst) explains the mechanism in two parts.
2. MECHANISM: a catalyst offers an alternative path between reactants and products with a LOWER activation energy. By the Arrhenius relation, even a modest drop in $E_a$ produces a large exponential rise in $k$.
3. SYMMETRY: the same alternative path is available to both the forward and reverse reactions, so BOTH rate constants increase by the same factor. Therefore the ratio $K_c = k_f / k_r$ is UNCHANGED.
4. The catalyst changes HOW FAST equilibrium is reached, not WHERE it lies — a recurring NEET trap.
5. Option A is the OPPOSITE of what catalysts do. Option C is a thermodynamic effect (true of LeChatelier-style shifts, not catalysts). Option D would require temperature change.
6. Consistency check with Equilibrium chapter: §6.8.3 confirms that catalysts do not change $K_c$, only kinetics — the two chapters agree.
_Source: NCERT Class 12 Chemistry Part 1, Ch 3, §3.4 (Catalyst, with Arrhenius diagram) + cross-reference Ch 6 §6.8.3, p. 17 + Ch 6 p. 21._
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