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 change when diamond converts to graphite is \( X \). The total enthalpy change for the complete oxidation of diamond to carbon dioxide is the sum of the enthalpy changes of the oxidation steps of both diamond and graphite. Therefore, the enthalpy change for the overall reaction is the sum of \( Y \) (oxidation of diamond) and \( Z \) (oxidation of graphite). Hence, \( X = Y + Z \).
Thus, the correct answer is \( \boxed{(4)} X = Y + Z \).