Question

$2N_{2}O\left(g\right)+O_2\left(g\right)\rightleftharpoons 4NO\left(g\right);\Delta H>0$

What will be the effect on equilibrium when volume of vessel increases?

• A. Equilibrium will shift backward
• B. No effect on equilibrium
• C. None of the above
• D. Equilibrium will shift forward

Answer 1

The correct option is D Equilibrium will shift forward

$2N_{2}O\left(g\right)+O_2\left(g\right)\rightleftharpoons 4NO\left(g\right);\Delta H>0$
$K_c=\frac{[NO{]}^4}{\left[N_{2}O{]}^2\right[O_2]}$
When volume of the vessel increases, number of moles per unit volume (i.e. molar concentration) of each reactant and product decreases. As there are $4$ concentration terms in the numerator but $3$ concentration terms in the denominator, to keep $K$ constant, the decrease in $\left[N_{2}O\right]$ and $\left[O_2\right]$ should be more i.e., equilibrium will shift in the forward direction.