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:
-
676.5
-
-676.5
-
-110.5
-
110 s
Solution
C.
-110.5
C(s) + O2 (g) → CO2 (g); ΔH = -393.5 kJ mol-1 ... (i)
CO + O2/2 → CO2 (g); ΔH = - 283.5 kJ mol-1 ....(ii)
On subtracting Eq. (ii) from Eq. (i), we get
C (s) + O2/2 (g) → CO (g)
ΔH = (-393.5 + 283.5) kJ mol-1 = - -110 kJ mol-1
