CBSE Class 12 · 2020 · Chemical KineticsShort Answer

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How will the rate of a reaction be affected when:
(a) the surface area of the reactant is reduced,
(b) a catalyst is added in a reversible reaction,
(c) the temperature of the reaction is increased?

Solution

(a) A smaller surface area gives fewer contact points for the reaction (for a solid reactant), so the rate decreases.
(b) The catalyst lowers the activation energy of the forward and the backward reaction equally — both speed up, equilibrium is attained faster, but the equilibrium position (K) is unchanged.
(c) Raising the temperature steeply increases the fraction of molecules with energy

\geq E_{a}

, so the rate increases (roughly doubling per 10 °C rise).

CBSE Class 12 Board · 2020 · Subjective

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