Question

A catalyst is a substance which:
(A) Increases the equilibrium concentration of the product
(B) Changes the equilibrium constant of the reaction
(C) Shortens the time to reach equilibrium
(D) Supplies energy to the reaction

Answer 1

Hint: Catalyst is a substance used in various chemical reactions. Understand the working of the catalyst mentioned in the chapter Surface chemistry. Based on the reaction mechanism you can predict the possible consequences and thus answer the question.

Complete step by step answer:
Catalysts use the process of adsorption to carry out chemical reactions. Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface called the adsorbent. This process creates a film of the adsorbate on the surface of the adsorbent.
Similar to surface tension, adsorption is also a consequence of surface energy. In a bulk material, all the bonding requirements of the atoms of the material are filled by adjacent atoms in the material.
However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and thereby attract the adsorbate particles.
Catalyst acts as the adsorbent and the reacting molecules act as the adsorbate. Due to this reaction mechanism, the time taken to attain equilibrium is reduced. This is the reason why catalysts are used to carry out chemical reactions.
So, the correct answer is “Option C”.

Note: Adsorption is considered to be an exothermic process which is explained theoretically and verified experimentally. As the particles come closer, the randomness in general decreases. Adsorption process is a feasible process at all temperatures.