Consider the chemical reaction:
`underset(("Green solution"))(Ni^(2+)(aq))+6NH_(3)(aq) hArr underset(("Blue solution"))([Ni(NH_(3))_(6)]^(2+)) (aq)`
When `H^(o+)(aq)` is added, the colour green is favoured. Use one or more of the following interpretations to answer the questions:
i. Some unreacted `Ni^(2+)(aq)` is present in the solution at equilibrium
ii. Some unreacted `NH_(3)(aq)` is present in the solution at equilibrium
iii. The colour change indicates new equilibrium conditions with reduced `[Ni(NH_(3))_(6)]^(2+)(aq)`
iv. The colour change indicates new equilibrium conditions with increased `[Ni(NH_(3))_(6)]^(2+)(aq)`.
The deepening of blue colour on addition of more `NH_(3)(aq)` supports interpretation(s).

Options

A. i only
B. i and iv only
C. i and ii only
D. ii and iv only

Answer

D

Explanation

Addition of `NH_(3)` causing more blue colour means reaction moving in the forward direction.
`rArr [Ni(NH_(3))_(6)]^(2+)` has increased and `Ni^(2+)` (unreacted) was present initially.