Question Description
A sample of ethanol (C2H5OH) was burned completely in a bomb calorimeter whose total heat capacity is 30.75 kJ/oC. The temperature of the calorimeter plus the contents increased from 25.6oC to 33.1oC.
Knowing that ethanol's heat of combustion is -1920 kJ/mol, calculate the mass of the sample (in g).

Final Answer

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30.75 kJ/deg x (33.1 - 25.6) = 230.625 kJ
230.625 kJ x 1 mol/1920 kJ = 0.120 moles
0.120 moles x 46 g/mol = 5.52 grams
There is no sign for the mass of the sample. The sign for the heat of combustion would be negative (exothermic)
