The heat of transition `(Delta H_(t))` of graphite into diamond would be, where
C (graphite) `+O_(2)(g)to CO_(2)(g) , Delta H =` x kJ
C (diamond) `+O_(2)(g)to CO_(2)(g) , Delta H =` y kJ

Options

A. `(x+y)kJ mol^(-1)`
B. `(x-y)kJ mol^(-1)`
C. `(y-x)kJ mol^(-1)`
D. `(x xx y)kJ mol^(-1)`

Answer

To find the heat of transition (ΔH_t) of graphite into diamond, we can use the given combustion reactions of graphite and diamond with oxygen. Let's break down the solution step by step.

### Step-by-Step Solution:

1. **Write the Combustion Reactions:**
- The combustion of graphite (C in its graphite form) is given as:
\[ C_{\text{(graphite)}} + O_2(g) \rightarrow CO_2(g) \quad \Delta H_1 = x \text{ kJ} \]
- The combustion of diamond (C in its diamond form) is given as:
\[ C_{\text{(diamond)}} + O_2(g) \rightarrow CO_2(g) \quad \Delta H_2 = y \text{ kJ} \]

2. **Reverse the Reaction for Diamond:**
- To find the heat of transition from graphite to diamond, we need to reverse the combustion reaction of diamond:
\[ CO_2(g) \rightarrow C_{\text{(diamond)}} + O_2(g) \quad \Delta H_2 = -y \text{ kJ} \]

3. **Combine the Reactions:**
- Now, we can add the two reactions together:
\[ C_{\text{(graphite)}} + O_2(g) \rightarrow CO_2(g) \quad \Delta H_1 = x \text{ kJ} \]
\[ CO_2(g) \rightarrow C_{\text{(diamond)}} + O_2(g) \quad \Delta H_2 = -y \text{ kJ} \]
- When we add these reactions, the \( CO_2(g) \) cancels out:
\[ C_{\text{(graphite)}} \rightarrow C_{\text{(diamond)}} \]
- The overall change in enthalpy (ΔH_t) for the transition from graphite to diamond is:
\[ \Delta H_t = \Delta H_1 + \Delta H_2 = x - y \text{ kJ} \]

4. **Final Result:**
- Therefore, the heat of transition (ΔH_t) of graphite into diamond is:
\[ \Delta H_t = x - y \text{ kJ} \]