Question

For the reaction\[A+2B\rightleftharpoons C~\], the expression for equilibrium constant is
(A) $\dfrac{[A]{{[B]}^{2}}}{[C]}$
(B) $\dfrac{[A][B]}{[C]}$
(C) $\dfrac{[C]}{[A]{{[B]}^{2}}}$
(D) $\dfrac{[C]}{2[A][B]}$

Answer 1

Hint: To solve this question we have to know about equilibrium constant. In an equilibrium reaction the rate constant of the reaction is given as the ratio of concentration of product to the concentration of reactant. Any coefficient of the reactant or product is used as the power of the concentration.

Complete Step by Step Solution:
The given reaction is \[A+2B\rightleftharpoons C~\].
Here one mole of reactant $A$ reacts with two moles of reactant $B$ to produce one mole of product $C$. It is not an unimolecular reaction as the change in number of moles is not zero. It is an equilibrium reaction as the product can also decompose to give back the reactants.

In an equilibrium reaction the rate constant of the reaction is given as the ratio of concentration of product to the concentration of reactant. Any coefficient of the reactant or product is used as the power of the concentration.

The equilibrium constant of the above equilibrium reaction is given as follows-
$\dfrac{[C]}{[A]{{[B]}^{2}}}$
Thus the correct option is C.

Note: An equilibrium reaction is that reaction where there is an equilibrium between the reactants and products of the reaction. Here the reaction can proceed in both the forward and backward directions that means reactants react to give product and again product can also break down into the corresponding reactants.