Q.12. Enthalpies of formation of COg,CO2g,N2OgandN2O4g

are –110 kJ mol-1, – 393 kJ mol-1, 81 kJ mol-1 and 9.7 kJ mol-1 respectively. Find the value of rH for the reaction:

N2O4g+3COgN2Og+3CO2g

NEETprep Answer:
Formation of CO2 from carbon and dioxygen gas can be represented as:
Cs+O2gCO2gfH=-393.5kJmol-1
(1 mole = 44 g)
Heat released on formation of 44 g CO2 = –393.5 kJ mol-1
Heat released on formation of 35.2 g CO2
=-393.5kJmol-144g×35.2g
=-314.8kJmol-1