[rcoleman]

The value of delta H for the reaction

C3H8(g) + 5O2(g) ---> 3CO2(g) + 4H2O(l)

delta H = -2220kJ\mol rxn

How much heat is given off when 33.0g of propane gas (C3H8) is burned at constant pressure?

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I first started off by calculating the number of moles present from propane:

33.0\44.094= ~0.7484 mol propane

I then was going to use the equation:

delta H = delta U + n*R*delta T

But there is no specified T, and delta U (the internal energy) could also be heat given off by a system correct?

So do I just take the T out of the equation and just plugin delta H, n(moles), and the value for R? Or am I using the wrong equation altogether for this type of calculation? Any help in the right direction would be greatly appreciated.

Thanks.

[plu]

You don't need any thermodynamic equations for this question.  Since you know that 2220 kJ is the amount of heat given off by the combustion of 1 mole of propane, you can calculate that 0.7484 moles of propane would give off 0.7484 x 2220 = 1.66 x 10³ kJ of heat.

[rcoleman]

Thank you sir.