Chem
posted by Shirley on .
2H2(g)+O2(g) > 2H2O(l)
delta H= 572kJ/mole of O2
Calculate the amount of heat evolved when 10g of hydrogen are burned in excess oxygen.
Can someone please explain step by step? =D

I worked this for you below. You didn't look or you don't understand? If you don't understand, go step by step and be specific about what you don't understand.

I looked at the solution from below but i do not understand where the 4g of H2 came from and why 572kJ x 10/4?
Would you mind explaining please? I'm quite new to this topic. 
Look at the equation.
2H2 + O2 ==> 2H2O
2 mols H2 react with 1 mol O2.
That's 4 g H2 (4*1 = 4) react with 32 g O2 (2*16=32).
So you would get 572 kJ if you had 32 g O2 or 4 g H2. Suppose you had 4 g H2. You would have
572 x 4/4 = ?
Suppose you had twice as much H2 (8 g H2)?
You would obtain twice as much or 572 x 2 = ? How do you get that? It's 572 x (8/4) = ?
If you have 10 g it's 572 x (10/4) = ?
What about apples? If apples cost 5.72 for 4 apples, how much will 10 apples cost? That's $5.72 x (10/4) = ? 
Thank you very much, I understand now (: