Question

Ethanol trapped in a gel is a common camping fuel. The thermochemical equation for the combustion of ethanol is : 

C2H5OH (l) + 3O2(g) → 2CO2(g) + 3H2O(g)

The ΔH for reaction (3) is -1368 kJ mol-1. What mass of ethanol must be burned to supply 350 kJ of heat? 

Answer 1

The molar mass of ethanol is 46.07 g/mol. Therefore, burning 46.07 g produces 1368 kJ of heat. Solving the proportion, the mass needed to supply 350 kJ is:

$\frac{46.07\ g\times350\ kJ}{1368\ kJ}=11.8\ g$

Answer: 11.8 g