# Given that DeltaH_"combustion"^@ for "propane" is -2043*kJ*mol^-1, what mass of propane is required to give 425*kJ?

Nov 9, 2015

${C}_{3} {H}_{8} \left(g\right) + 5 {O}_{2} \left(g\right) \rightarrow 3 C {O}_{2} \left(g\right) + 4 {H}_{2} O \left(g\right) + 2043$ $k J$
So if 425 kJ of energy are evolved, then $\frac{425 \cdot k J}{2043 \cdot k J}$ $\cong \frac{1}{5}$. Thus, approximately, 1/5 of a mole of propane must be combusted with stoichiometric oxygen to evolve this amount of energy. You can calculate the molar quantity of propane in grams, and you need approx. 1/5 of this.