What happens when a molten mixture of `K_(2)FeO_(4)` and `K_(2)CrO_(4)` is acidified?

Options

A. `FeO_(4)^(2-)` is converted to `H_(2)FeO_(4)`
B. `CrO_(4)^(2-)` is reduced to `Cr^(3+)` liberating `O_(2)`
C. `CrO_(4)^(2-)` is converted to `Cr^(3+)`
D. `FeO_(4)^(2-)` is reduced to `Fe^(3+)` liberating `O_(2)`.

Explanation

To solve the problem of what happens when a molten mixture of \( K_2FeO_4 \) and \( K_2CrO_4 \) is acidified, we will analyze the reactions of both compounds with sulfuric acid (\( H_2SO_4 \)).

### Step 1: Reaction of \( K_2FeO_4 \) with \( H_2SO_4 \)

1. **Write the reaction**:
\[ K_2FeO_4 + H_2SO_4 \rightarrow Fe_2(SO_4)_3 + O_2 + K_2SO_4 + H_2O \]

2. **Balance the reaction**:
- The balanced equation is:
\[ 2 K_2FeO_4 + 10 H_2SO_4 \rightarrow 2 Fe_2(SO_4)_3 + 3 O_2 + 4 K_2SO_4 + 10 H_2O \]

3. **Identify oxidation states**:
- In \( K_2FeO_4 \), the oxidation state of iron (Fe) is +6.
- In \( Fe_2(SO_4)_3 \), the oxidation state of iron (Fe) is +3.

4. **Determine the change**:
- The iron is reduced from +6 to +3, indicating a gain of electrons (reduction).

### Step 2: Reaction of \( K_2CrO_4 \) with \( H_2SO_4 \)

1. **Write the reaction**:
\[ K_2CrO_4 + H_2SO_4 \rightarrow K_2Cr_2O_7 + K_2SO_4 + H_2O \]

2. **Balance the reaction**:
- The balanced equation is:
\[ K_2CrO_4 + H_2SO_4 \rightarrow K_2Cr_2O_7 + K_2SO_4 + H_2O \]

3. **Identify oxidation states**:
- The oxidation state of chromium (Cr) in both \( K_2CrO_4 \) and \( K_2Cr_2O_7 \) is +6.

4. **Determine the change**:
- There is no change in the oxidation state of chromium, indicating no oxidation or reduction occurs.

### Conclusion

When the molten mixture of \( K_2FeO_4 \) and \( K_2CrO_4 \) is acidified:
- \( K_2FeO_4 \) is reduced to \( Fe_2(SO_4)_3 \) and liberates oxygen.
- \( K_2CrO_4 \) remains unchanged in oxidation state and does not liberate oxygen.

Thus, the main reaction is the reduction of \( K_2FeO_4 \) to \( Fe_2(SO_4)_3 \) with the liberation of oxygen.

### Final Answer
The correct statement is that \( K_2FeO_4 \) is reduced to \( Fe_2(SO_4)_3 \) liberating oxygen, while \( K_2CrO_4 \) does not undergo any change.

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