`Mg_(3)N_(2)(s)+H_(2)O overset(R.T.)to P darr+Q uarr`
Excess 'Q' gas does not form coloured complex with:

Options

A. `Ni^(2+)(aq.)`
B. `Zn^(2+)(aq.)`
C. `Cr^(3+)(aq.)`
D. `Cu^(2+)(aq.)`

Explanation

To solve the question, we need to analyze the reaction between magnesium nitride (Mg₃N₂) and water (H₂O) and identify the products formed. Then, we will determine which gas (Q) does not form a colored complex with a specific ion.

### Step-by-Step Solution:

1. **Identify the Reaction**:
- The reaction of magnesium nitride with water can be represented as:
\[ \text{Mg}_3\text{N}_2(s) + 6\text{H}_2\text{O}(l) \rightarrow 3\text{Mg(OH)}_2(s) + 2\text{NH}_3(g) \]
- Here, magnesium hydroxide (Mg(OH)₂) is the precipitate (P), and ammonia (NH₃) is the gas evolved (Q).

2. **Identify the Excess Gas**:
- In this case, the excess gas (Q) is ammonia (NH₃).

3. **Determine the Complex Formation**:
- We need to find out which ion does not form a colored complex with ammonia when NH₃ is in excess.
- Common ions that form colored complexes with ammonia include copper (Cu²⁺), cobalt (Co²⁺), and nickel (Ni²⁺).

4. **Identify the Ion that Forms a Colorless Complex**:
- Zinc (Zn²⁺) is known to form a colorless complex with ammonia:
\[ \text{Zn}^{2+} + 4\text{NH}_3 \rightarrow \text{[Zn(NH}_3\text{)}_4]^{2+} \]
- This complex is colorless due to the absence of unpaired electrons in the Zn²⁺ ion, making it diamagnetic.

5. **Conclusion**:
- Therefore, the excess gas (Q) does not form a colored complex with zinc ion (Zn²⁺).

### Final Answer:
The excess gas (Q) does not form a colored complex with zinc ion (Zn²⁺).