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 dissolving more `Ni(NO_(3))_(2)` supports interpretation (s).

Options

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

Explanation

To solve the problem, we need to analyze the given chemical equilibrium and the effects of adding `H^(o+)(aq)` and `Ni(NO3)2` on the equilibrium state.

### Step-by-Step Solution:

1. **Identify the Reaction and Equilibrium**:
The reaction is:
\[ \text{Ni}^{2+}(aq) + 6\text{NH}_3(aq) \rightleftharpoons [\text{Ni(NH}_3)_6]^{2+}(aq) \]
The green solution corresponds to `Ni^(2+)`, and the blue solution corresponds to the complex ion `[\text{Ni(NH}_3)_6]^{2+}`.

2. **Effect of Adding `H^(o+)(aq)`**:
When `H^(o+)(aq)` is added, it favors the formation of `Ni^{2+}` ions, shifting the equilibrium to the left. This results in a green color being favored, indicating that the concentration of the complex ion decreases.

3. **Interpretation of the Color Change**:
The deepening of the blue color upon adding more `Ni(NO3)2` suggests that the concentration of `Ni^{2+}` ions is increasing. This addition disturbs the equilibrium, causing the reaction to shift to the right to form more of the blue complex.

4. **Evaluating the Interpretations**:
- **Interpretation i**: "Some unreacted `Ni^{2+}` is present in the solution at equilibrium."
- This is **true** because adding `Ni(NO3)2` increases the concentration of `Ni^{2+}`, which means some `Ni^{2+}` was unreacted initially.

- **Interpretation ii**: "Some unreacted `NH3` is present in the solution at equilibrium."
- This is **false** because at equilibrium, all `NH3` would have reacted to form the complex, leaving no unreacted `NH3`.

- **Interpretation iii**: "The color change indicates new equilibrium conditions with reduced `[Ni(NH3)6]^{2+}`."
- This is **false** because the deepening blue color indicates an increase in the concentration of the complex ion, not a reduction.

- **Interpretation iv**: "The color change indicates new equilibrium conditions with increased `[Ni(NH3)6]^{2+}`."
- This is **true** because the addition of `Ni(NO3)2` increases the concentration of the complex ion, leading to a deeper blue color.

5. **Conclusion**:
The interpretations that hold true are:
- i: Some unreacted `Ni^{2+}` is present in the solution at equilibrium.
- iv: The color change indicates new equilibrium conditions with increased `[Ni(NH3)6]^{2+}`.

### Summary of Interpretations:
- True: i and iv
- False: ii and iii