When `CO_(2)` is passed into aqueous:

Options

A. `Na_(2)CrO_(4)` solution, its yellow colour change to orange
B. `K_(2)MnO_(4)` solution,it disproportionates to `MnO_(4)` and `MnO_(2)`
C. `Na_(2)Cr_(2)O_(7)` solution its orange colour changes to green
D. `KMnO_(4)` solution, its pink colour chanhe to green

Explanation

To solve the question regarding the effects of passing CO₂ into aqueous solutions of different compounds, we will analyze each of the four statements provided.

### Step-by-Step Solution:

1. **Statement 1: CrO₄²⁻ solution changes from yellow to orange.**
- When CO₂ is passed into an aqueous solution of chromate ions (CrO₄²⁻), it reacts with water to form carbonic acid (H₂CO₃), which makes the solution acidic. In acidic conditions, chromate ions convert to dichromate ions (Cr₂O₇²⁻), which are orange in color.
- **Conclusion:** This statement is **correct**.

2. **Statement 2: K₂MnO₄ solution disproportionates to MnO₄⁻ and MnO₂.**
- When K₂MnO₄ is treated with CO₂ and water, it undergoes a disproportionation reaction. The manganese in K₂MnO₄ (which is in the +6 oxidation state) is oxidized to MnO₄⁻ (which is in the +7 oxidation state) and reduced to MnO₂ (which is in the +4 oxidation state).
- The balanced reaction can be written as:
\[ 3 K₂MnO₄ + 4 CO₂ + 2 H₂O \rightarrow 2 KMnO₄ + 4 KHCO₃ + MnO₂ \]
- **Conclusion:** This statement is **correct**.

3. **Statement 3: Na₂Cr₂O₇ solution changes from orange to green.**
- When Na₂Cr₂O₇ (sodium dichromate) is reacted with CO₂, it does not convert to a green solution. Instead, it remains in the dichromate form, which is orange. The chromate form (CrO₄²⁻) is yellow, but the solution does not turn green in this reaction.
- **Conclusion:** This statement is **incorrect**.

4. **Statement 4: KMnO₄ solution changes from pink to green.**
- KMnO₄ (potassium permanganate) is a strong oxidizing agent and is typically pink in color. However, it does not react with CO₂ in aqueous solution to change its color. Therefore, the pink color remains unchanged.
- **Conclusion:** This statement is **incorrect**.

### Final Summary:
- **Correct Statements:** 1 and 2
- **Incorrect Statements:** 3 and 4