`underset(("Coloured"))(P("soln.")) overset(Air) to underset(("Coloured"))(Q("soln.")) overset(KOH)to underset((ppt.)" (Insoluble in both excess NaOH and excess "NH_(3)" solution)")(Rdarr)`
then P contains:

Options

A. `Cu^(2+)(aq.)`
B. `Fe^(2+)(aq.)`
C. `Cu^(2+)(aq.)`
D. `Ni^(2+)(aq.)`

Answer

To determine what P contains, we will analyze the information given in the question step by step.

### Step 1: Identify the nature of solution P
- The problem states that solution P is colored. In chemistry, colored solutions often indicate the presence of transition metal ions, which have partially filled d-orbitals that allow for d-d transitions.

**Hint:** Look for transition metals when identifying colored solutions.

### Step 2: Determine the possible ions in solution P
- Given that the solution is colored, we can consider common colored ions such as Fe²⁺ (ferrous ion) and Fe³⁺ (ferric ion). Among these, Fe²⁺ is known to produce a green-colored solution.

**Hint:** Recall the common colors associated with transition metal ions.

### Step 3: Analyze the reaction with air
- The question states that when solution P (which we suspect contains Fe²⁺) is exposed to air, it converts to solution Q, which is also colored. This indicates that Fe²⁺ is oxidized to Fe³⁺ in the presence of air.

**Hint:** Oxidation reactions often involve the loss of electrons, leading to a higher oxidation state.

### Step 4: Identify solution Q
- The conversion of Fe²⁺ to Fe³⁺ results in a yellow-colored solution (solution Q). This confirms that solution P contains Fe²⁺ ions.

**Hint:** Check the color changes associated with oxidation states of transition metals.

### Step 5: Analyze the reaction with KOH
- The problem states that solution Q (which contains Fe³⁺) reacts with KOH to form a precipitate (R). The precipitate formed is ferric hydroxide (Fe(OH)₃), which is a brown precipitate.

**Hint:** Remember that hydroxides of transition metals often precipitate out of solution.

### Step 6: Confirm the solubility of the precipitate
- The question mentions that the precipitate is insoluble in both excess NaOH and excess NH₃. This is characteristic of ferric hydroxide, confirming our previous conclusions.

**Hint:** Precipitate solubility can help confirm the identity of the compound formed.

### Conclusion
Based on the analysis, we conclude that solution P contains Fe²⁺ ions.

### Final Answer
P contains: **Fe²⁺ ions**.

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