Question asking for energy of combustion?

Question

Calculate the energy of combustion per gram of Olive Oil (kJ/g) if 30.7 mL of water is placed in the test tube and the temperature changes from 22.9 ºC to 44.6 ºC. The initial mass of the spirit burner is 204.60 g and the final mass is 204.51g. State your answer with correct significant digits.

Answer 1

q = mC∆T

q = ?

m = 30.7 g (assuming a density of 1g/ml for water)

C = 4.184 J/g/deg

∆T = 44.6 - 22.9 = 21.7 deg

q = (30.7 g)(4.184 J/g/deg)(21.7 deg) = 2787 J = 2.787 kJ

mass of oil consumed (combusted) = 204.60 - 204.51 = 0.090 g

Energy of combustion per gram = 2.787 kJ/0.090 g = 30.966 kJ/g = 31.0 kJ/g (to 3 sig. figs.)