Diphenylamine reagent gives a deep blue colour with a solution. It contains

Options

A. `Sn^(2+)`
B. `NO_(2)^(-)`
C. `NO_(3)^(-)`
D. `Fe^(3+)`

Answer

To determine which of the given ions (Sn²⁺, NO₂⁻, NO₃⁻, Fe³⁺) gives a deep blue color with diphenylamine reagent, we need to analyze the properties of each ion concerning their ability to act as oxidizing agents.

### Step-by-step Solution:

1. **Understand the Role of Diphenylamine**:
Diphenylamine is a reagent that is commonly used to detect the presence of oxidizing agents. When it reacts with certain oxidizing agents, it produces a characteristic deep blue color.

**Hint**: Remember that diphenylamine is sensitive to oxidizing agents.

2. **Identify the Oxidizing Agents**:
An oxidizing agent is a substance that can accept electrons from another substance, thereby oxidizing it. We need to identify which of the given ions can act as oxidizing agents.

3. **Analyze Each Ion**:
- **Sn²⁺ (Tin(II) ion)**: This is a reducing agent, as it can lose electrons to become Sn⁴⁺. Therefore, it cannot produce a deep blue color with diphenylamine.

**Hint**: Reducing agents donate electrons and do not produce the characteristic color.

- **NO₂⁻ (Nitrite ion)**: This ion can act as an oxidizing agent. It can accept electrons and thus can react with diphenylamine to produce a deep blue color.

**Hint**: Look for ions that can accept electrons; these are typically oxidizing agents.

- **NO₃⁻ (Nitrate ion)**: This ion is also an oxidizing agent, although it is less reactive than NO₂⁻. It can also react with diphenylamine to give a deep blue color.

**Hint**: Consider that many nitrate compounds can act as oxidizing agents.

- **Fe³⁺ (Ferric ion)**: This ion is a well-known oxidizing agent and will also react with diphenylamine to produce a deep blue color.

**Hint**: Transition metals in higher oxidation states are often good oxidizing agents.

4. **Conclusion**:
From the analysis, we find that NO₂⁻, NO₃⁻, and Fe³⁺ can all produce a deep blue color with diphenylamine, while Sn²⁺ cannot. Therefore, the ions that give a deep blue color with diphenylamine are NO₂⁻, NO₃⁻, and Fe³⁺.

### Final Answer:
The solution contains NO₂⁻, NO₃⁻, and Fe³⁺.