What is the mass of acetylene ( C₂H₂ ) gas produced when 32 g of a commercial sample of calcium carbide ( CaC₂ ), which is 75 % pure, reacts completely with an excess of water? (Atomic mass of Ca = 40 , C = 12 , H = 1 ) [ CaC₂ + 2H₂O Ca(OH)₂ + C₂H₂ ]

Step-by-step solution

Mass of pure CaC₂ in the sample = 32 75 100 = 24 g Molar mass of CaC₂ = 40 + 2 12 = 64 g/mol Moles of CaC₂ reacting = 24 64 = 3 8 mol The balanced chemical equation is: CaC₂ + 2H₂O Ca(OH)₂ + C₂H₂ From the stoichiometry of the reaction, 1 mol of CaC₂ produces 1 mol of C₂H₂ . Moles of C₂H₂ produced = 3 8 mol Molar mass of C₂H₂ = 2 12 + 2 1 = 26 g/mol Mass of C₂H₂ produced = 3 8 26 = 9.75 g Answer: 9.75 g