Question

The enthalpy of combustion of methane, graphite and dihydrogen at 298 K are, –890.3 kJ mol^–1 –393.5 kJ mol^–1, and –285.8 kJ mol^–1 respectively. Enthalpy of formation of CH_4(g) will be

(i) –74.8 kJ mol^–1 (ii) –52.27 kJ mol^–1

(iii) +74.8 kJ mol^–1 (iv) +52.26 kJ mol^–1.

Answer 1

According to the question,

Thus, the desired equation is the one that represents the formation of CH_{4 (g)} i.e.,

Enthalpy of formation of CH_4(g) = –74.8 kJ mol^–1

Hence, alternative (i) is correct.