A catalyst is a substance which
1. increases the equilibrium concentration of the product
2. increases the rate of forward reaction and reduces the rate of backward reaction
3. supplies energy to the reaction
4. reduces the time taken to reach the equilibrium
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 4 (reduces the time taken to reach the equilibrium)
A catalyst speeds up a reaction by providing an alternative pathway with a lower activation energy. It takes part in the reaction but is regenerated unchanged at the end.
So a catalyst reduces the time taken to reach equilibrium.
Why the other options are incorrect
Option (1) 1 — Incorrect. A catalyst does not change the equilibrium constant, so the equilibrium concentration of the product stays the same.
Option (2) 2 — Incorrect. It speeds up both the forward and the backward reactions; it never slows the backward one.
Option (3) 3 — Incorrect. It supplies no energy; it lowers the activation energy by changing the reaction path.
NCERT (2026-27 edition):
Effect of Catalyst – “A catalyst is a substance which increases the rate of a reaction without itself undergoing any permanent chemical change. …”
“… It is also found that a catalyst does not change the equilibrium constant of a reaction rather, it helps in attaining the equilibrium faster, that is, it catalyses the forward as well as the backward reactions to the same extent so that the equilibrium state remains same but is reached earlier.”