Heat of combustion of diamond `=-91 kcal "mol"^(-1)` and heat of combustion of graphite `=-94 K` cal `"mol"^(-1)`. Find the heat of transition of diamond to graphite in kcal `"mol"^(-1)`.

Answer

To find the heat of transition of diamond to graphite, we can use the given heats of combustion for both substances. The heat of transition can be calculated using the following formula:

\[ \Delta H_{\text{transition}} = \Delta H_{\text{combustion (graphite)}} - \Delta H_{\text{combustion (diamond)}} \]

### Step-by-Step Solution:

1. **Identify the given values:**
- Heat of combustion of diamond, \(\Delta H_{\text{combustion (diamond)}} = -91 \, \text{kcal/mol}\)
- Heat of combustion of graphite, \(\Delta H_{\text{combustion (graphite)}} = -94 \, \text{kcal/mol}\)

2. **Set up the equation for the heat of transition:**
\[ \Delta H_{\text{transition}} = \Delta H_{\text{combustion (graphite)}} - \Delta H_{\text{combustion (diamond)}} \]

3. **Substitute the values into the equation:**
\[ \Delta H_{\text{transition}} = (-94 \, \text{kcal/mol}) - (-91 \, \text{kcal/mol}) \]

4. **Simplify the equation:**
\[ \Delta H_{\text{transition}} = -94 + 91 \]
\[ \Delta H_{\text{transition}} = -3 \, \text{kcal/mol} \]

5. **Interpret the result:**
The heat of transition of diamond to graphite is \( -3 \, \text{kcal/mol} \). This indicates that the transition from diamond to graphite is an exothermic process.

### Final Answer:
The heat of transition of diamond to graphite is \( -3 \, \text{kcal/mol} \).

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