Feb 15, 2015

The answer is $\text{9273 J/g}$ of ${\text{S}}_{8}$ are evolved in this reaction.

If you look at the balanced chemical equation

${S}_{8 \left(s\right)} + 8 {O}_{2 \left(g\right)} \to 8 S {O}_{2 \left(g\right)}$

you'll notice that 1 mole of ${\text{S}}_{8}$ produces 8 moles of ${\text{SO}}_{2}$, which explains why the heat of reation is $\text{-2374 kJ}$.

The heat of formation for 1 mole of $S {O}_{2}$ is $\text{-296.81 kJ/mol}$. If you have 8 moles of ${\text{SO}}_{2}$, you'll get 8 times as much heat evolved for 1 mole of ${\text{S}}_{8}$. This means that the heat produced by 1 mole of ${\text{S}}_{8}$ will be equal to

${\text{-296.81 kJ/mol" * ("8 moles SO"_2)/("1 mole S"_8) = "-2374 kJ/mol of S}}_{8}$

As a result, the heat evolved per gram of ${\text{S}}_{8}$ will be

$\text{-2374 kJ/mol" * ("1 mole S"_8)/("256 g") = "-9.273 kJ/g}$ of ${\text{S}}_{8}$, which is equal to

$\text{-9273 J/g}$ of ${\text{S}}_{8}$