1. 2C₂H₂(g) + 5O₂(g) → 4CO₂(g) + 2H₂O(g) ∆H = -2599.1 kJ a) How many moles of O₂ react to produce 4000.0 kJ of energy? (be sure to round to the correct number of sig figs and include units)
b) If 27.0 g of H₂O are produced, how much energy (in kJ) is given off?

2. 2H₂(g) + O₂(g) → 2H₂O(l) ∆H = -571.5 kJ
a) If 1143.0 kJ of energy are given off in the above reaction, how many molecules of H₂ react?
b) How many grams of H₂O are made when 571.5 kJ of energy are released?

Explanations please

Thanks!