Question

The heats of combustion of carbon and carbon monoxide are –393.5 and –283.5 kJ mol⁻¹, respectively. The heat of formation (in kJ) of carbon monoxide per mole is :(a) –676.5 (b) – 110.5(c) 110.5 (d) 676.5

Answer 1

Combustion of Carbon:

C + O2 → CO2 ; ΔH1 = – 393.5 kJ / mole

Combustion of Carbon Monoxide:

CO + ½O2 → CO2 ; ΔH2 = – 283.5 kJ / mole

Formation of Carbon Monoxide:

C + ½O2 → CO ; ΔH

ΔH = ΔH1 - ΔH2

= –393.5 –(–283.5)

= –393.5 + 283.5

= –110 kJ/mole

The correct option is C.