Calculating heat of combustion of ethanol?

Answer 1

Measure a volume of water and place it in a thin metal container with a lid, stirrer and thermometer.

Pour some ethanol in a spirit lamp and weigh the spirit lamp with ethanol and cap.

Ignite the lamp and place it under the metal container to heat up the water. Insulate to minimize heat losses.

When the temperature rises by, say, 15 degrees stop the lamp and close it (to avoid further evaporation of ethanol).

Weigh the lamp again to calculate the mass of ethanol used up.

The energy transfered to water can be measured using the equation Q = mc(T2-T1), where:

Q = energy supplied, in J

m = mass of water, in Kg

c = specific heat capacity of water (find it in a data book), in J/KgK

T2 - T1 = change in temperature, in K, in our case 15 degrees

By having the mass of ethanol used, say x grams, one can say the energy, Q, was supplied by burning by burning x grams. By simple proportion, one can find the energy that would be given on burning one mole (46g) of ethanol. This would be the heat of combustion in KJ/mol.