# Homework Help: How much heat is liberated from the complete combustion

1. May 29, 2005

### ~angel~

The complete combustion of RDX is 2C3H6N6O6 + 302 --> 6H2O + 6CO2 + 6N2.

How much heat is liberated from the complete combustion of 10g of RDX?

delta H values: H20 = -286, CO2 = -394, RDX = +65 (all in kJ/mol)

I thought it'll be (6*-286 + 6*-394) - (2*65)
= -4210 kJ/mol

Then divide that by the amount of moles in 100g. But I end up with this massive number which is wrong. I'm not sure whether to take into acount the 2 moles of RDX reacting when finding the amount of moles in 100g as well.

Thanks.

2. May 30, 2005

### vsage

Why did you divide it when the units you found for $$\Delta H$$ implies you multiply by the number of moles? Also, remember the number you found is actually the heat liberated per *2* mol of RDX.

Last edited by a moderator: May 30, 2005