Question

If \[ \text{C(diamond)} \rightarrow \text{C(graphite)} + X \, \text{kj mol}^{-1} \] \[ \text{C(diamond)} + \text{O}_2(g) \rightarrow \text{CO}(g) + Y \, \text{kj mol}^{-1} \] \[ \text{C(graphite)} + \text{O}_2(g) \rightarrow \text{CO}(g) + Z \, \text{kj mol}^{-1} \] At constant temperature. Then:

• A. \( X = Y + Z \)
• B. \( X - Y = Z \)
• C. \( X = Y - Z \)
• D. \( X = Y + Z \)

Hint:

The enthalpy changes for reactions can be combined if the reactions occur sequentially, such as in the oxidation of diamond and graphite to form carbon dioxide.

Answer 1

The Correct Option is D

The energy difference between diamond and graphite is \( X \). The overall enthalpy change for oxidizing diamond to carbon dioxide is equivalent to the sum of the enthalpy changes for the oxidation of diamond and graphite separately. Consequently, the enthalpy change for the complete reaction is \( Y \) (diamond oxidation) plus \( Z \) (graphite oxidation). Therefore, \( X = Y + Z \).
This leads to the conclusion that \( \boxed{(4)} X = Y + Z \) is the correct relation.