U3-3-2 - Enthalpy of Combustion
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What is Eh?
Heat energy (in kJ)
What is c?
Specific heat capacity of water (4.18)
What is ∆T?
Change in temperature Difference between starting and final temperature of water
What is m?
Mass of substance heated, in kg (NOT mass of fuel!) For water, 1000 cm3 = 1 kg
Suggest the greatest source of error in this experiment
Heat loss to surroundings due to lack of heat shield
Suggest a piece of apparatus that can minimise heat loss to surroundings during combustion
Heat shield (or bomb calorimeter)
The energy released when 1 mole of a substance undergoes complete combustion.
Enthalpy of combustion
Ethanol has GFM = 46 g. Burning 4.6 g released 136.7 kJ. Write an expression to calculate the enthalpy of combustion for ethanol.
Use proportion to scale up energy to 1 mole of fuel 1 mole has mass = GFM
This equation does not represent the enthalpy of combustion. Why?
Must be complete combustion (products CO2 and H2O)
Enthalpy of combustion
The energy released when 1 mole of a substance undergoes complete combustion.