Question

When 6 g carbon is burnt in a sufficient amount of oxygen, the heat evolved is $x$ kJ. The heat of combustion of carbon is :

• A. $x$ kJ
• B. $2x$ kJ
• C. $4x$ kJ
• D. none

Answer 1

Answer: (B)

$2x$ kJ

$C_{\left(s\right)}+O_2\left(g\right)\to C{O}_2\left(g\right)$

Moles of carbon $=\frac{6}{12}=\frac{1}{2}$

For $\frac{1}{2}$ mole, $x$ kJ heat evolved.

$\therefore$ Heat of combustion $=$ $2x$ kJ mol${}^{-1}$