PYQ NEET- Chemical Equilibrium-1 L-9

Question: Given the reaction between 2 gases represented by $A_2$ and $B_2$ to give the compound $A B_{(g)}$,#

$$ \mathrm{A}2(\mathrm{~g})+\mathrm{B}{2(\mathrm{~g})} \rightleftharpoons 2 \mathrm{AB}_{(\mathrm{g})} $$

At equilibrium, the concentration of $A_2=3.0 \times 10^{-3} \mathrm{M}$, of $B_2=4.2 \times 10^{-3} \mathrm{M}$, of $A B=2.8 \times 10^{-3} \mathrm{M}$

If the reaction takes place in a sealed vessel at $527^{\circ} \mathrm{C}$, then the value of $K_C$ will be

A) 2.0

B) 1.9

C) 0.62

D) 4.5

Answer: 0.62#

Solution:#

$\begin{aligned} & \mathrm{A}2(\mathrm{~g})+\mathrm{B}{2(\mathrm{~g})} \rightleftharpoons 2 \mathrm{AB}{(\mathrm{g})} \ & \mathrm{K}{\mathrm{C}}=\frac{[A B]^2}{\left[A_2\right]\left[B_2\right]} \ & =\frac{\left(2.8 \times 10^{-3}\right)^2}{3 \times 10^{-3} \times 4.2 \times 10^{-3}} \ & =0.62\end{aligned}$