What will be the colour of the solution when `Mn(OH)_(2)` is treated with concentrated `HNO_(3) and `sodium bismuthate (or red lead or lead dioxide)?

Options

A. Yellow
B. Purple
C. Green
D. Blue

Answer

To determine the color of the solution when manganese hydroxide (Mn(OH)₂) is treated with concentrated nitric acid (HNO₃) and sodium bismuthate (NaBiO₃), we can follow these steps:

### Step 1: Identify the Reactants
We have manganese hydroxide (Mn(OH)₂), concentrated nitric acid (HNO₃), and sodium bismuthate (NaBiO₃).

### Step 2: Understand the Oxidation Process
Manganese in Mn(OH)₂ is in the +2 oxidation state (Mn²⁺). When treated with concentrated nitric acid, which is a strong oxidizing agent, Mn²⁺ can be oxidized to a higher oxidation state.

### Step 3: Reaction with Sodium Bismuthate
Sodium bismuthate (NaBiO₃) also acts as an oxidizing agent. In acidic medium, it can oxidize Mn²⁺ to MnO₄⁻ (permanganate ion), where manganese is in the +7 oxidation state.

### Step 4: Write the Balanced Chemical Equation
The balanced equation for the reaction can be represented as follows:
\[ 2 \text{Mn}^{2+} + 14 \text{H}^+ + 5 \text{NaBiO}_3 \rightarrow 2 \text{MnO}_4^- + 5 \text{Bi}^{3+} + 5 \text{Na}^+ + 7 \text{H}_2\text{O} \]

### Step 5: Identify the Color of the Product
The product formed in this reaction is the permanganate ion (MnO₄⁻), which is known to have a distinct purple color.

### Conclusion
Therefore, when manganese hydroxide is treated with concentrated nitric acid and sodium bismuthate, the color of the resulting solution will be **purple**.

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