posted by Lulu on .
How do I go about doing this question?
How much heat energy is involved when 5.58g of Fe metal reacts with excess oxygen to produce Fe2O3? Do you need the equation, and if so, what would tha be? Fe + O2 > Fe2O3? I don't think that is right though. And also, do you find moles of Fe? Thanks.
Yes, you need the equation. The one you wrote is a start, but you need to BALAMCE it. Do you know how to do that?
I do, but I wasn't sure if I even was doing the right thing, so I didn't bother. But ok so, the equation would be: 2 Fe + 1/2 O2 > Fe2O3 right...and then what do I do? Heat of formation and do the Hess' law equation of products-reactants? Thanks.
The way you have it written the oxygens do not balance. It is actually:
4Fe + 3O2 > 2Fe2O3. (or, 2Fe + 1.5O2 > Fe2O3.
So, basically 2 moles of Fe goes to form one mole of Fe2O3. Then, you must calculate how many moles of Fe you start with, and then you know how many moles of Fe2O3 you form. Then you can use the standard enthalpy of formation of Fe2O3, which is per mole.