4.20 g of a hydrocarbon, C20H16, were burned in excess oxygen in a constant-volume calorimeter surrounded by

Question

4.20 g of a hydrocarbon, C20H16, were burned in excess oxygen in a constant-volume calorimeter surrounded by 1250. g of water. As a result the temperature of the water and the calorimeter rose from 21.3 oC to 26.1 oC. The heat capacity of the calorimeter was 251.040 J/oC.





Calculate DE (kJ/mol) for the combustion of the hydrocarbon based on these readings.





Enter a numeric answer only, do not include units in your answer.

Answer 1

Energy released by the reaction = 4.8 * 250 = 1200 J (using 2 sig figs).

One mole is 256g....4.2 g is 1.6E-2 moles.

Ergo...1200/1.6E-2 = 73000 J/mole or 73 kJ/mole