Question

When the system $\mathrm{A}+\mathrm{B}\rightleftharpoons \mathrm{C}+\mathrm{D}$ is at equilibrium?

• A. the forward reaction has stopped.
• B. both the forward and the reverse reactions have stopped.
• C. the reverse reaction has stopped.
• D. neither the forward nor the reverse reaction has stopped.

Answer 1

The correct option is D

neither the forward nor the reverse reaction has stopped.

Expalantion for correct option:

D. neither the forward nor the reverse reaction has stopped.

Chemical equilibrium

• In the case of chemical equilibrium, the rates of the forward and reverse reactions become equal.
• In this case, the concentrations of the reactants and the products remain constant.
• Chemical equilibrium is dynamic in nature wherein concentrations of both reactant and product change constantly with equal speed.
• It is a reversible reaction in which a change in a substance can be reversed by changing the conditions.
• Thus, neither the forward nor the reverse reaction has stopped.

Example of Chemical equilibrium:

• In the formation of Nitrous oxide, there exist a chemical equilibrium wherein reactants and products are present in the same phases.

${\mathrm{N}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\rightleftharpoons 2\mathrm{NO}\left(\mathrm{g}\right)$

Hence, option D is the correct choice i.e. neither the forward nor the reverse reaction has stopped.