Question

The heat of combustion of carbon to $C{O}_2$ is -393.5 kJ/mol. The heat released upon formation of 35.2 g of $C{O}_2$ from catbon and oxygen gas will be :

• A. +315 kJ/mole
• B. -31.5 kJ/mole
• C. -315 kJ/mole
• D. +31.5 kJ/mole

Answer 1

Answer: (C)

-315 kJ/mole

Heat of combustion for $1$ mole of $C{O}_2$ is $-393.5KJ$

Number of moles in $35.2g$ of $C{O}_2=\frac{35.2}{44}=0.8$mole

Thus heat of combustion for $0.8$ mole of $C{O}_2$ is $-393.5\times 0.8=-315KJ$