Question
The heat of combustion of $$C,S$$ and $$C{S_2}$$ are $$ - 393.3\,kJ, - 293.7\,kJ$$ and $$ - 1108.76\,kJ.$$ What will be the heat of formation of $$C{S_2}?$$
A.
$$ - 128.06\,kJ$$
B.
$$ + 970\,kJ$$
C.
$$ + 1108.7\,kJ$$
D.
$$ + 12\,kJ$$
Answer :
$$ - 128.06\,kJ$$
Solution :
\[\begin{align}
& C+2S\to C{{S}_{2}} \\
& \Delta H=\sum{\Delta {{H}_{P}}-\sum{\Delta {{H}_{R}}}} \\
& \,\,\,\,\,\,\,\,\,=-1108.76-\left[ -393.3+2\times \left( -293.7 \right) \right] \\
& \,\,\,\,\,\,\,\,\,=-1108.76+393.3+587.4 \\
& \,\,\,\,\,\,\,\,\,=-128.06\,kJ \\
\end{align}\]