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 

CH4_(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.