Could I get help with this enthalpy problem.

Question

2H2(g) + O2(g) → 2H2O(l) ∆H = -572kJ

a. How much heat is evolved from 1 mole of water?

b. How much heat is evolved when 4.03g hydrogen are reacted with excess oxygen?

c. How much heat is evolved from 186g of oxygen are reacted with excess hydrogen?

d. How much heat is evolved from 2.0 X 10 8 L at 1atm and 25 o C. Hint: Moles= PV/RT where R=0.0821 and T= 273 + o C

*I really need to learn the steps to solve problems like this but have not found any examples.

Answer 1

2H₂(g) + O₂(g) ==> 2H₂O(l) ∆H = -572kJ

This tells us that for 2 moles H2 producing 2 moles H2O, it liberates 572 kJ of energy

a) 1 mol H₂O x 572 kJ/2 mol H₂O = 286 kJ evolved

b) 4.03 g H₂ x 1 mol H₂/2.0 g x 572 kJ/2 mol H₂ = 576 kJ

c) 186 g O₂ x 1 mol O₂/32 g x 572 kJ/1 mol O₂ = 3320 kJ

d) 2.0x10⁸ L of WHAT? Liters of H₂, O₂ ????