Consider the following combustion reactions for graphite and diamond - VCE - SSCE Chemistry - Question 7 - 2011 - Paper 1

To determine the enthalpy change for the conversion of graphite to diamond, we can use the provided combustion reactions.

1. The enthalpy change of combustion for graphite is given as ΔH = -393 kJ mol⁻¹.
2. The enthalpy change of combustion for diamond is given as ΔH = -395 kJ mol⁻¹.

The reaction we are interested in is:

$C(graphite) → C(diamond)$

Using Hess's Law, we can calculate the enthalpy change:

$ΔH = ΔH_{combustion ext{ (graphite)}} - ΔH_{combustion ext{ (diamond)}}$

Substituting the values:

$ΔH = (-393 ext{ kJ mol}^{-1}) - (-395 ext{ kJ mol}^{-1})$

This simplifies to:

$ΔH = -393 + 395 = +2 ext{ kJ mol}^{-1}$

Thus, the enthalpy change for the conversion of graphite to diamond is +2 kJ mol⁻¹.