C6H14 + 19/2 O2 -> 6 CO2 + 7H2O enthalpy change = -4163 kJ

a) if 0.537 mol of carbon dioxide is produced in the reaction represented by the equation above, how much heat is released by the reaction?

Enthalpy change = 0.537 mol CO2 x -4163kJ/6 mol CO2
=-373 kJ

B) If 25.0 kg of hexane is burned in sufficient oxygen, how much heat will be released?

Enthalpy change = 25000g C6H14 x 1 mol C6H14/86 g x -4163 kJ/1 mol C6H14
= -1.21 x 10^6 kJ

C) what mass of hexane is required to produce 1.0E5 kJ of heat by complete combustion?

1.0E5 kJ = m x 1 mol/86g x 4163/1mol
1.0E kJ = m x -48.45 kJ/g
1.0E kJ/-48.45 kJ/g = m
-2.0E3 g = m
I know this one's wrong since mass can't be negative...

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1. The first two are right.
The last one I would do this way.
4163 kJ/mol x # mols = 1E5 kJ.
Solve for mols. Then g = mols x molar mass.

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2. Sorry, how would you solve for mols? I feel like this should be obvious, but ...

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3. 4163 kJmol x #mols = 1E5 kJ.
# mols = 1E5/4163 = ?

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