Question

As pressure is increased, what will happen to the following reactions?

Match the column:

Column - I	Column - II
(P) $PC{l}_5\left(g\right)\rightleftharpoons PC{l}_3\left(g\right)+C{l}_2\left(g\right)$	(1) Shift to forward
(Q) $2N{O}_2\left(g\right)\rightleftharpoons N_2{O}_4\left(g\right)$	(2) Shift to backward
(R) $H_2\left(g\right)+I_2\left(g\right)\rightleftharpoons 2HI\left(g\right)$	(3) No effect
(S) $aA\left(g\right)+bB\left(g\right)\rightleftharpoons cC\left(g\right)$	(4) Cannot predict

• A. 1 2 3 4
• B. 2 1 3 4
• C. 2 1 4 3
• D. 4 3 1 2

Answer 1

Answer: (B)

2 1 3 4

An increase in pressure will cause the reaction to shift in the direction that reduces pressure, that is the side with the fewer number of gas molecules.

For reaction (P), the equilibrium will shift to backward as number of moles of gaseous reactants is less than the number of moles of gaseous products.

For reaction (Q), the equilibrium will shift to forward as number of moles of gaseous reactants is more than the number of moles of gaseous products.

For reaction (R), the equilibrium will not shift in any direction as number of moles of gaseous reactants is equal to the number of moles of gaseous products.

For reaction (S), the direction of the shift in the equilibrium cannot be predicted as number of moles of gaseous reactants and gaseous products is not given.