The heats of combustion of carbon and carbon monoxide are –393.5 and –283.5

• Chemical Thermodynamics

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:

1. 676.5
2. –676.5
3. –110.5
4. 110.5

Solution

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.