Q51 / 200 · NEET 2024 · Chemistry

For the reaction $2 \mathrm{~A} \rightleftharpoons \mathrm{B}+\mathrm{C}, \mathrm{K}_{\mathrm{C}}=4 \times 10^{-3}$. At a given time, the composition of reaction mixture is: $[\mathrm{A}]=[\mathrm{B}]=[\mathrm{C}]=2 \times 10^{-3} \mathrm{M}$. Then, which of the following is correct?

  • A
    Reaction has a tendency to go in forward direction.
  • Correct answer
    B
    Reaction has a tendency to go in backward direction.
  • C
    Reaction has gone to completion in forward direction.
  • D
    Reaction is at equilibrium.

Solution

$2 \mathrm{~A} \rightleftharpoons \mathrm{B}+\mathrm{C}, \mathrm{K}_{\mathrm{C}}=4 \times 10^{-3}$ At a given time $\mathrm{t}, \mathrm{Qc}_{\mathrm{c}}$ is to be calculated and been compared with $\mathrm{K}_{\mathrm{c}}$. $\begin{aligned} & \mathrm{Q}_{\mathrm{C}}=\frac{[\mathrm{B}][\mathrm{C}]}{[\mathrm{A}]^2}=\frac{\left(2 \times 10^{-3}\right)\left(2 \times 10^{-3}\right)}{\left(2 \times 10^{-3}\right)^2} \\ & \mathrm{Q}_{\mathrm{C}}=1 \end{aligned}$ As $Q_c\gtK_c$, so reaction has a tendency to move backward.

Hence, the correct answer is option: 'B'.

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