Question

The following two reactions:
i. `PCl_(5)(g) hArr PCl_(3)(g)+Cl_(2)(g)`
(ii) `COCl_(2)(g) hArr CO(g)+Cl_(2)(g)`
are simultaneously in equilibrium in a container at constant volume. A few moles of `CO(g)` are later introduced into the vessel. After some time, the new equilibrium concentration of
A. `PCl_(5)` will remain unchanged
B. `Cl_(2)` will be greater
C. `PCl_(5)` will become greater
D. `PCl_(5)` will become less

Answer 1

Correct Answer - D
`PCl_(5)(g) hArr PCl_(3)(g)+Cl_(2)(g) ..(i)`
`COCl_(2)(g) hArr CO(g)+Cl_(2)(g) …(ii)`
Addition `CO(g)` shifts reaction (ii) in the backward direction. This in turn decreases `Cl_(2)(g)` which causes relation (i) to shift in forward direction and therefore concentration of `PCl_(5)` will decrease.