Okay so you have calculated the amount of energy produced , this can be used to work out the molar enthalpy change (this is basically the enthalpy change given out by one mole of the reactant).
NOTE:
To calculate the molar enthalpy change, you need to know the equations moles = mass / Mr (if unsure of this equation, click here) and molar enthalpy change = energy produced / moles. For example...
0.9g of methylated spirit produces 6510J of heat energy, work out the heat produced per mole. (The Mr of methylated spirit is 44.6)
- First, work out the amount of energy transferred...
We know that 6510J of heat energy was produced, this means 6510J of energy was transferred... this needs to be converted into kJ (as the unit or enthalpy change is kJ/mol)... 6.510kJ
- Next, find out how many moles of fuel produced this heat...
moles = mass / Mr
= 0.9 / 44.6
= 0.02 moles
- Now, divide the amount of heat energy produced by the amount of moles...
6.510 / 0.02 = 325.5 kJ/mol
The end (:
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