Question

In the following reaction:
$N{O}_{(}g)+C{l}_{2\left(g\right)}\rightleftharpoons 2NOC{l}_{(}g)$
it is observed that equilibrium is not attained and the rate of forward reaction is greater than rate of backward reaction. Which of the following is true for the reaction?

• A. $K_p=Q_p$
• B. $Q_p>K_p$
• C. $Q_p<K_p$
• D. $Q_p=0$

Answer 1

Answer: (C)

$Q_p<K_p$

The equilibrium constant helps in predicting the direction in which a given reaction will proceed at any stage. For this purpose, we calculate the reaction quotient Q. The reaction quotient, Q (Qc with molar concentrations and Qp with partial pressures) is defined in the same way as the equilibrium constant Kc except that the concentrations in Qc are not necessarily equilibrium values.

Consider the equation:

$aA+bB\rightleftharpoons cC+dD$

$Q_c=\frac{C{]}^c[D{]}^d}{\left[A{]}^a\right[B{]}^b}$

If $Q_p<K_p$, the reaction will proceed in the direction of the products (forward reaction).