Question

Which of the following reactions proceed at low pressure?

• A. $N_2+3H_2\rightleftharpoons 2N{H}_3$
• B. $H_2+I_2\rightleftharpoons 2HI$
• C. $PC{l}_5\rightleftharpoons PC{l}_3+C{l}_2$
• D. $N_2+O_2\rightleftharpoons 2NO$

Answer 1

The correct option is C $PC{l}_5\rightleftharpoons PC{l}_3+C{l}_2$

At low pressure, as per the Le Chatelier's principle system tries to increase pressure to attain equilibrium. The reaction proceeds in a direction where number of moles are more. In the following given reaction,
$PC{l}_5\rightleftharpoons PC{l}_3+C{l}_2$
L.H.S has 1 mole and R.H.S has 2 moles
Thus, decrease in the pressure helps the reaction move in forward direction.