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Posted by on Sunday, February 10, 2013 at 11:33pm.

Are my answers correct?

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...


Thanks in advance!

  • Chemistry - , Sunday, February 10, 2013 at 11:49pm

    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.

  • Chemistry - , Monday, February 11, 2013 at 12:01am

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

  • Chemistry - , Monday, February 11, 2013 at 12:28am

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

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