ENTHALPY OF COMBUSTION ΔHc

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Presentation transcript:

ENTHALPY OF COMBUSTION ΔHc Enthalpy of Combustion: the heat energy given out when one mole of a substance burns in oxygen. Always exothermic, so ΔHc always negative

MEASURING ENTHALPY OF COMBUSTION Bomb Calorimeter: substance is burnt in a sealed container, heat released during the reaction goes into the water, can calculate ΔH by calculating ΔT of the water.

MEASURING ENTHALPY OF COMBUSTION School Lab: consists of simple set up of a spirit burner positioned below a container of water. Burn a substance under a known quantity of water. Measure the mass of the spirit burner before and after burning for a period of time. Use the change in mass to determine how many moles of substance has been burnt. Measure ΔT of the water. Calculate ΔH using equations.

ENTHALPY OF COMBUSTION ΔHc A spirit burner used 1.00g of methanol to raise the temperature of 100.0g water in a metal can from 25°C to 55°C. Assuming the heat capacity of water is 4.18 J.g-1.°C-1, calculate the molar enthalpy of combustion of methanol in kJ.mol-1.

ENTHALPY OF COMBUSTION ΔHc Ethanol was placed in a spirit burner and used to heat 200cm3 of water in a copper can. When the temperature of the water had increased by 5°C, the mass of the burner and ethanol had decreased by 0.36g. Calculate the enthalpy of combustion of ethanol.