For the allotropic change represented by the equation: . If 6.0 g of diamond and 6.0 g of graphite i — Thermodynamics and Thermochemistry Chemistry Question
Question
For the allotropic change represented by the equation: $\text{C(graphite)} \to \text{C(diamond)}; \Delta H = +1.9\text{ kJ}$. If 6.0 g of diamond and 6.0 g of graphite is burnt completely in separate experiments, then the heat liberated will be higher by
Answer: C
💡 Solution & Explanation
Diamond has a higher enthalpy than graphite by 1.9 kJ/mol. Burning it releases this extra stored energy. Moles burnt = $6.0\text{ g} / 12\text{ g/mol} = 0.5\text{ mol}$. Extra heat from diamond = $0.5\text{ mol} \times 1.9\text{ kJ/mol} = 0.95\text{ kJ}$. Therefore, it's 0.95 kJ higher in the case of diamond.
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