Question

$28g$ of $N_2$ and $6g$ of $H_2$ were kept at ${400}^{o}C$ in $1$ litre vessel, the equilibrium mixture contained $27.54g$ of ${NH}_3$. The appropriate value of $K_c$ for the above reaction can be (in ${mole}^{-2}{litre}^2$)

• A. $75$
• B. $50$
• C. $25$
• D. $100$

Answer 1

Answer: (A)

$75$

$N_2+3H_2\rightleftharpoons 2{NH}_3$

$\left(g\right)$ $\left(g\right)$ $\left(g\right)$

At $28g$ ${6g}^1$ $0g$

$t=0$

$\Downarrow$ $\Downarrow$ $\Downarrow$

1 mol 3 mol 0 mol

$A$ $1-\alpha$ $3-3\alpha$ $2\alpha$

$t=t_{eq}$

Given ($2\alpha$ moles) weight $=27.54$

$2\alpha =1.62$

$\alpha =0.81$

$0.19$ $0.57$ $1.62$

$K_C=\frac{{\left(1.62\right)}^2}{{\left(0.57\right)}^3\times \left(0.19\right)}\approx 75$