Question

Energy released on combustion of $7\, g$ of ethene is ____$kJ$.
(The combustion enthalpy of ethene $\left(\Delta H ^{\circ}\right)=\left.-1411\, kJ\, mol ^{-1}\right)$

Answer 1

$C _{2} H _{4}+3 O _{2} \longrightarrow 2 CO _{2}+2 H _{2} O$
Moles $C _{2} H _{4}=\frac{7}{28}=0.25$ mole
Energy released on combustion of $1$ mole of ethene $=1411 \,kJ$
Hence, energy released on combustion of $0.25\, mol$ ethene $=0.25 \times(1411)$
$=352.75 \,kJ$