Question

The enthalpies of combustion of carbon and carbon monoxide are – 393.5 and – 283 kJ mol–1 respectively. The enthalpy of formation of carbon monoxide per mole is

• A. 110.5 KJ
• B. 676.5 kJ
• C. – 676.5 kJ
• D. – 110.5 kJ

Answer 1

Answer: (D)

– 110.5 kJ

Answer 2

$C(s) + O_{2}(g) \rightarrow CO_{2}(g);\Delta$H = – 393.5 kJ mol–1

.... (1)

CO(g) + $\frac{1}{2}$O2(g) $\rightarrow$ CO2(g) ; $\Delta$H = – 283 kJ mol–1

.... (2)

On subraction equation (2) from equation (1), we get C(s) + O2(g) $\rightarrow$CO(g) ; $\Delta$H = – 110.5 kJ mol–1.

The enthalpy of formation of carbon monoxide per mole = – 110.5 kJ mol–1.