Using the equation S + O2 = SO2 + 297 kJ, calculate how much sulfur is burned to release 742.5 kJ of heat.

Let us write the thermochemical equation of the sulfur combustion reaction:

S + O2 = SO2 + 297 kJ

According to the reaction equation, 297 kJ of heat is formed per 1 mol of S, therefore 742.5 kJ of heat was formed from 742.5 / 297 = 2.5 mol of S.

Thus, the amount of sulfur substance that has reacted is:

v (S) = 2.5 (mol),

and the mass of sulfur that has entered the reaction:

m (S) = v (S) * M (S) = 2.5 * 32 = 80 (g).