Question

If the heat of formation of $C{O}_2$ is -393 kJ. The amount of heat evolved in the formation of 0.176 kg of $C{O}_2$ is:

• A. - 1357.9 kJ
• B. - 1275.9 kJ
• C. - 1572.0 kJ
• D. - 1165.5 kJ

Answer 1

The correct option is C - 1572.0 kJ

Heat of formation is amount of heat absorbed or evolved when 1 mole of substance is formed from its elements.
given, mass of $C{O}_2=0.176kg=176g$
Molecular weight of $C{O}_2=1mole$ of $C{O}_2=44g$
$\underset{12g}{C}+\underset{2\times 16g}{O_2}⟶\underset{44g}{C{O}_2}-393kJ$
$\because$ Heat evolvedm when 44g of $C{O}_2$ is produced $=-393kJ$
$\therefore$ Heat evolved when 176 g of $C{O}_2$ is produced
$=-\frac{393}{44}\times 176$
$=-1572kJ$