Thank you for reporting, we will resolve it shortly
Q.
The standard molar heat of formation of ethane, $CO_2$ and water are respectively $-21.1, -94.1$ and $-68.3\, kcal$. The standard molar heat of combustion of ethane will be
Given,
(i) $2 C +3 H _{2} \longrightarrow C _{2} H _{6} ; \Delta H=-21.1$
(ii) $C + O _{2} \longrightarrow CO _{2} ; \Delta H=-94.1$
(iii) $H _{2}+\frac{1}{2} O _{2} \longrightarrow H _{2} O ; \Delta H=-68.3$
Eqs. 2 (ii) $+3$ (iii) - (i)
$C _{2} H _{6}+\frac{3}{2} O _{2} \longrightarrow 2 CO _{2}+3 H _{2} O$
$\Delta x =2(-94.1)+3(-68.3)-(-21.1)$
$=-372\, kcal$