`H_2O_2` oxidises `K_4Fe(CN)_6`

Options

A. In neutral solution
B. In acidic solution
C. In non-polar solvent
D. In alkaline solution

Explanation

To solve the problem of how hydrogen peroxide (H₂O₂) oxidizes potassium ferrocyanide (K₄[Fe(CN)₆]) in an acidic medium, we can break down the process into several steps:

### Step 1: Identify the Reactants
The reactants involved in this reaction are:
- Hydrogen peroxide (H₂O₂)
- Potassium ferrocyanide (K₄[Fe(CN)₆])

### Step 2: Determine the Medium
The reaction occurs in an acidic medium. This is important because the acidity can influence the oxidation state of iron in potassium ferrocyanide.

### Step 3: Oxidation State of Iron
In K₄[Fe(CN)₆], iron is in the +2 oxidation state (Fe²⁺). In the presence of H₂O₂, which acts as an oxidizing agent, iron can be oxidized to the +3 oxidation state (Fe³⁺).

### Step 4: Write the Half-Reactions
1. **Oxidation Half-Reaction**: The oxidation of Fe²⁺ to Fe³⁺ can be represented as:
\[ \text{Fe}^{2+} \rightarrow \text{Fe}^{3+} + e^- \]

2. **Reduction Half-Reaction**: The reduction of H₂O₂ in acidic medium can be represented as:
\[ \text{H}_2\text{O}_2 + 2\text{H}^+ + 2e^- \rightarrow 2\text{H}_2\text{O} \]

### Step 5: Balance the Overall Reaction
To balance the overall reaction, we need to ensure that the number of electrons lost in the oxidation half-reaction equals the number of electrons gained in the reduction half-reaction. Since the oxidation of Fe²⁺ involves the loss of 1 electron and the reduction of H₂O₂ involves the gain of 2 electrons, we can multiply the oxidation half-reaction by 2:
\[ 2\text{Fe}^{2+} \rightarrow 2\text{Fe}^{3+} + 2e^- \]

### Step 6: Combine the Half-Reactions
Now, we can combine the balanced half-reactions:
\[ 2\text{Fe}^{2+} + \text{H}_2\text{O}_2 + 2\text{H}^+ \rightarrow 2\text{Fe}^{3+} + 2\text{H}_2\text{O} \]

### Step 7: Include Potassium and Cyanide Ions
Since we started with K₄[Fe(CN)₆], we should include the potassium and cyanide ions in the final balanced equation:
\[ K_4[Fe(CN)_6] + H_2O_2 + 2H^+ \rightarrow K_4[Fe(CN)_6] + 2Fe^{3+} + 2H_2O \]

### Final Balanced Reaction
The final balanced reaction in acidic medium can be summarized as:
\[ K_4[Fe(CN)_6] + H_2O_2 + 2H^+ \rightarrow K_4[Fe(CN)_6] + 2Fe^{3+} + 2H_2O \]