Statement - I. By increasing the temperature C.N. of CsCl changes from 8 : 8 to 6 : 6. Statement - II. Temperature also influences the C.N. of solid.

Options

A. If both Statement- I and Statement- II are true, and Statement - II is the correct explanation of Statement– I.
B. If both Statement - I and Statement - II are true but Statement - II is not the correct explanation of Statement – I.
C. If Statement - I is true but Statement - II is false.
D. If Statement - I is false but Statement - II is true.

Answer

To solve the problem, we need to analyze the two statements provided and determine their validity and relationship.

### Step 1: Analyze Statement I
**Statement I:** By increasing the temperature, the coordination number (C.N.) of CsCl changes from 8:8 to 6:6.

- **Coordination Number (C.N.):** The coordination number of an ion in a crystal lattice refers to the number of nearest neighbor ions surrounding it. In the case of CsCl, at lower temperatures, the coordination number is 8:8, meaning each Cs ion is surrounded by 8 Cl ions and vice versa.
- **Effect of Temperature:** As temperature increases, thermal energy disrupts the ionic bonds in the crystal lattice. This can lead to a change in the arrangement of ions, resulting in a decrease in the coordination number.

**Conclusion for Statement I:** This statement is correct. The coordination number of CsCl can indeed change from 8:8 to 6:6 with an increase in temperature.

### Step 2: Analyze Statement II
**Statement II:** Temperature also influences the C.N. of solid.

- **Influence of Temperature on C.N.:** It is well-known in solid-state chemistry that temperature affects the stability of the crystal lattice. As temperature increases, the vibrational energy of the ions increases, which can weaken the ionic bonds and lead to changes in the coordination number.

**Conclusion for Statement II:** This statement is also correct. Temperature does influence the coordination number of solids.

### Step 3: Relationship Between Statements
- Since both statements are correct, we need to determine if Statement II correctly explains Statement I.
- The explanation provided in Statement II about how temperature affects coordination number directly supports the change observed in Statement I.

**Final Conclusion:** Both statements are correct, and Statement II correctly explains Statement I.

### Summary of the Solution:
- **Statement I:** Correct (C.N. of CsCl changes from 8:8 to 6:6 with temperature increase).
- **Statement II:** Correct (Temperature influences the C.N. of solids).
- **Relationship:** Statement II explains Statement I.