How much heat is produced by the combustion of 125 g of acetylene?

The reaction of acetylene with oxygen is as follows:

\({{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{2}}}{\rm{(g) + }}\frac{{\rm{5}}}{{\rm{2}}}{{\rm{O}}_{\rm{2}}}{\rm{(g)}} \to {\rm{2C}}{{\rm{O}}_{\rm{2}}}{\rm{(g) + }}{{\rm{H}}_{\rm{2}}}{\rm{O(l)}}\)

Here, in the above reaction, one mole of acetylene produces -1301.1 kJ heat. The number of moles of acetylene is calculated as:

\({\bf{Number of moles = }}\frac{{{\bf{Given mass}}}}{{{\bf{Molar mass}}}}\)

\(\begin{array}{c}{\rm{Number of moles = }}\frac{{{\rm{125}}}}{{{\rm{26}}{\rm{.04}}}}\\{\rm{ = 4}}{\rm{.80 mol}}\end{array}\)

If 1 mol of acetylene produces -1301.1 kJ, then 4.8 mol of acetylene produces:

\(\begin{array}{l}{\rm{ = 1301}}{\rm{.1 \times 4}}{\rm{.8 }}\\{\rm{ = 6245}}{\rm{.28 kJ }}\\{\rm{ = 6}}{\rm{.25 kJ}}\end{array}\)