`CrO_(4)^(2-)underset(pH=Y)overset(pH=X)(hArr)Cr_(2)O_(7)^(-2)` The pH values of (X) and (Y) are respectively

Options

A. 5, 9
B. 6, 5
C. 8, 6
D. 7, 7

Answer

To solve the problem, we need to understand the relationship between the chromate ion (CrO4^2-) and the dichromate ion (Cr2O7^2-) in relation to pH.

### Step-by-Step Solution:

1. **Understanding the Species**:
- The chromate ion (CrO4^2-) is stable in alkaline (basic) conditions.
- The dichromate ion (Cr2O7^2-) is stable in acidic conditions.

2. **Identifying pH Conditions**:
- When the pH is low (acidic), the equilibrium favors the formation of dichromate ions (Cr2O7^2-).
- When the pH is high (alkaline), the equilibrium favors the formation of chromate ions (CrO4^2-).

3. **Assigning pH Values**:
- Let pH = X correspond to the condition where CrO4^2- is present, which is in basic conditions. Therefore, pH X > 7.
- Let pH = Y correspond to the condition where Cr2O7^2- is present, which is in acidic conditions. Therefore, pH Y < 7.

4. **Conclusion**:
- From the above analysis, we can conclude that:
- pH X (for CrO4^2-) is greater than 7.
- pH Y (for Cr2O7^2-) is less than 7.

Thus, the pH values of X and Y are respectively greater than 7 and less than 7.

### Final Answer:
- pH X > 7
- pH Y < 7