Question

The following reaction attains equilibrium at high temperature.
$N_2\left(g\right)+2H_{2}O\left(g\right)+\text{heat}\rightleftharpoons 2NO\left(g\right)+2H_2\left(g\right)$
The yield of $NO$ is affected by

• A. Increasing the nitrogen concentration
• B. Decreasing the hydrogen concentration
• C. Compressing the reaction mixture
• D. None of these

Answer 1

Answer: (A), (B), (C)

Compressing the reaction mixture

When a system is in equilibrium if any external change was implied, the equilibrium will shift its direction to nullify the external effect. This is called Le Chatlier's principle.

In the given reaction,
$N_2\left(g\right)+2H_{2}O\left(g\right)+\text{heat}\rightleftharpoons 2NO\left(g\right)+2H_2\left(g\right)$

Increase in concentration of reactant will shift the equilibrium toward product side, hence increase in $N_2$ concentration will increase the concentration of $NO$.

Decrease in concentration of product will favour the equilibrium toward product side, hence decrease in concentration of $H_2$ will increase the concentration of $NO$.

When the pressure of the reaction mixture is increased, to nullify this effect equilibrium will shift in the direction where the moles of gaseous substance is less. Hence the equilibrium will shift to reactant side, so the $NO$ concentration decreases.
Thus, in all three conditions the concentration of $NO$ is affected.