Question

The combustion of 5.00 grams of c2h6(g), at constant pressure releases 259 kj of heat. what is δh for the reaction: 2c2h6(g) + 7o2(g) => 4co2(g) + 6h2o(l)?

Answer 1

The molar mass of C2H6 is 28 g/mol, so the number of moles is:

moles C2H6 = 5 / 28 = 0.179 mol

From the equation, there are 2 moles of C2H6, therefore the heat of reaction is:

δh = (259 kj / 0.179 mol) * 2 mol

δh = 2900 kJ = 2.9 MJ