1) Balanced chemical reaction
4NH3 + 5O2 ---> 4NO + 6H2O
2) Molar ratios
4 mol NH3 : 5 mol O2 : 4 mol NO : 6 mol H2O
3) Convert 8.45 g of O2 to moles
moles = mass in grams / molar mass = 8.45 g / 32.0 g/mol = 0.264 mol O2
4) Proportion
5 mol O2 / 6 mol H2O = 0.264 mol O2 / x
=> x = 0.264 mol O2 * 6 mol H2O / 5 mol O2 = 0.3168 mol H2O
5) Convert 0.3168 mol H2O in grams
mass = molar mass * number of moles
molar mass H2O = 18.0 g/mol
mass = 18.0 g/mol * 0.3168 mol = 5.7024 g ≈ 5.70 g
Answer: 5.70 g