Determine the mass of oxygen necessary to react with 2.3 moles of HCl

Balanced equation: 4HCl + O₂ → 2Cl₂ + 2H₂O

mole ratio of HCl : O₂ is 4 : 1

∴ if moles of HCl = 2.3 mol

then mol of O₂ = 2.3 mol : 4

= 0.575 mol

mass of O₂ = moles of O₂ * molar mass of O₂

= 0.575 mol * (16 * 2) g/mol

= 18.4 g