Question

Nitrogen and hydrogen are added to a $5$ litre flask under pressure. The flask was sealed and heated. The equilibrium mixture contained $19.0g$ of ammonia, $0.16g$ of hydrogen and $3.4g$ of nitrogen. Calculate the equilibrium constant, $K_c$ of the reaction:
$N_2\left(g\right)+3H_2\left(g\right)\rightleftharpoons 2{NH}_3\left(g\right)$

Answer 1

Nitrogen and hydrogen are added to a $5$ litre flask under pressure. The flask was sealed and heated. The equilibrium mixture contained $19.0g$ of ammonia, $0.16g$ of hydrogen and $3.4g$ of nitrogen.
$N_2\left(g\right)+3H_2\left(g\right)\rightleftharpoons 2{NH}_3\left(g\right)$
The molecular weights of nitrogen, hdrogen and ammonia are 28 g/mol, 2 g/mole and 17 g/mole respectively.
$\left[N_2\right]=\frac{\text{3.4 g}}{\text{28 g/mol}\times \text{5 L}}=\text{0.02429 M}$
$\left[H_2\right]=\frac{\text{0.16 g}}{\text{2 g/mol}\times \text{5 L}}=\text{0.016 M}$
$\left[N{H}_3\right]=\frac{\text{19.0 g}}{\text{17 g/mol}\times \text{5 L}}=\text{0.2235 M}$
$K_c=\frac{[N{H}_3{]}^2}{\left[N_2\right][H_2{]}^3}$
$K_c=\frac{(\text{0.2235 M}{)}^2}{\text{0.02429 M}\times (\text{0.016 M}{)}^3}$

The equilibrium constant, $K_c=5.02\times {10}^5{mol}^{-2}{L}^2$