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A simple copper calorimeter was filled with 150 cm3 of cold water. This was heated up using a spirit burner containing butan-1-ol. 0.433 grams of alcohol was burnt in order to raise the temperature by 18.7 ºC. What was the measured enthalpy of combustion of butan-1-ol?
C4H9OH = 74
\ number of moles of butan-1-ol burnt = 0.433/74 = 0.00585
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Heat energy (in J) = 4.18 × mass of solution (in g) × temperature change (in °C) |
Heat absorbed by water = 4.18 × 150 × 18.7 = 11725 J = 11.7 kJ
\ DHc (butan-1-ol) = - 11.7/0.00585 = - 2000 kJ mol-1 (last figure has been rounded off)