You can find the amount of heat evolved in the combustion of carbonby carrying o

Question

You can find the amount of heat evolved in the combustion of carbonby carrying out the reaction in a combustion calorimeter. Supposeyou burn 0.300 g of C (graphite) in an excess of O2 (g) to give CO2(g).
The temperature of the calorimeter, which contains 775 g ofwater, increases from 25.00 ºC to 27.38 ºC. The heatcapacity of the calorimeter is 893 J/K. What quantity of heat isevolved per mole of C?
The temperature of the calorimeter, which contains 775 g ofwater, increases from 25.00 ºC to 27.38 ºC. The heatcapacity of the calorimeter is 893 J/K. What quantity of heat isevolved per mole of C?

Explanation / Answer

The heat given out by the combustion of carbon is absorbed bythe water and the calorimeter. Heat absorbed by water = mass * specific heat * temperaturedifference                                       =775 g * 4.18 J/(g.C) * (27.38 -25)                                       =7710J . Heat absorbed by the calorimeter = Heat capacity * temperaturedifference                                                    = 893 J/ K * (27.38 - 25)                                                    = 2125.3 J . So total heat evolved by 0.3 g of C = 7710 J + 2125.3 J =9835.3 J . Moles of C = mass / atomic mass                   =0.3 g / 12.01 g/mol                   =0.025 moles . Heat evolved per mole of C = 9835.3 J / 0.025 moles                                           = 393412 J/mol                                            =393.4 kJ/mol

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