Question

For the reaction, $A+B\rightleftharpoons 3C$, at ${25}^{0}C$, 3 litre vessel contains 1, 2, 4 moles of $A,B$ and $C$ respectively. If $K_c$ for the reaction is 10, the reaction will proceed in:

• A. forward reaction
• B. backward direction
• C. in either direction
• D. in equilibrium

Answer 1

The correct option is B backward direction

$[\left[C\right]=\frac{4}{3};\left[A\right]=\frac{1}{3};\left[B\right]=\frac{2}{3}]$

Quotient, $Q=\frac{{\left[C\right]}^3}{\left[A\right]\left[B\right]}=\frac{4^3\times 3\times 3}{3^3\times 1\times 2}=10.66$
Since, $K_c=10$.

Thus, $Q$ must decrease to attain value of $K_c$ and therefore, $\left[C\right]$ must decrease or $\left[A\right]$ or $\left[B\right]$ must increase, i.e., backward direction.

Hence, option B is correct.