Question

The heat of combustion of methane is $-880kJ$ ${mol}^{-1}$. If $3.2g$ of methane is burnt _______ of heat is evolved.

• A. $88kJ$
• B. $264kJ$
• C. $176kJ$
• D. $440kJ$

Answer 1

Answer: (C)

$176kJ$

Molecular mass of methane $=16gm/mol$.

So $\text{moles of methane =}$ $\frac{\text{mass of methane}}{\text{molecular weight of methane}}$

=> $moles=$ $\frac{3.2}{16}$ $=0.2$

Hence, $\text{energy evolved =}$ $\text{(moles of methane)}\times$$\text{(heat of combustion)}$

=> Heat evolved $=-0.2\times 880=-176kJ$

Hence, the answer is option $C$.