Question

A reversible reaction A⇌B reaches equilibrium when:

• A. Forward rate = Reverse rate
• B. All A is converted to B
• C. Temperature is zero
• D. Pressure is infinite

Hint:

Chemical equilibrium is dynamic — reactions don’t stop, but occur at equal rates in both directions, so concentrations remain constant.

Answer 1

The Correct Option is A

In a reversible chemical reaction such as:
\[ \text{A} \rightleftharpoons \text{B} \]
equilibrium is achieved when the rate of the forward reaction becomes equal to the rate of the reverse reaction.
This is the fundamental definition of chemical equilibrium in dynamic systems.
At equilibrium:
- The concentrations of A and B remain constant (not necessarily equal).
- Both the forward and reverse reactions continue to occur, but at the same rate.
- There is no net change in the amounts of A and B over time.
Analysis of options:
(1) Forward rate = Reverse rate — Correct. This is the condition for dynamic equilibrium.
(2) All A is converted to B — Incorrect. At equilibrium, some amount of both A and B is generally present.
(3) Temperature is zero — Incorrect. At absolute zero, molecular motion stops, and no reaction occurs.
(4) Pressure is infinite — Incorrect and physically unrealistic; pressure does not define equilibrium condition directly.