I'm doing some revision and am trying to work the 2005 HSC multiple choice question "The heat of combustion of butan-1-ol is 2676kJ mol-1. What is the value of the heat of combustion in kJ g-1? Having a bit of trouble. Thanks! 
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Heat of combustion HSC question Help! (1 Viewer)
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fishrushed
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You convert the kJ/mol into kJ/g.
So we find the molar mass of butanol, which is around 74 (I think). Then to change from kJ/mol to kJ/g we divide by the molar mass.
It might be easier to visualise if we write out the units like an equation.
(kJ/mol x mol/g = kJ/g) note that if we replace a multiplication sign by a divide sign we flip the fraction we were multiplying by.
So, 2676/74 = 36.162.... That should be the answer, unless I did something wrong
So we find the molar mass of butanol, which is around 74 (I think). Then to change from kJ/mol to kJ/g we divide by the molar mass.
It might be easier to visualise if we write out the units like an equation.
(kJ/mol x mol/g = kJ/g) note that if we replace a multiplication sign by a divide sign we flip the fraction we were multiplying by.
So, 2676/74 = 36.162.... That should be the answer, unless I did something wrong
fishrushed
Member
- Joined
- Apr 20, 2012
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- 96
- Gender
- Male
- HSC
- 2013
No worries