what mass of water must react with calcium carbide for 3.9g of acetylene gas to form?
CaC2 + 2HOH ==> Ca(OH)2 + C2H2
mols C2H2 = grams/molar mass
Using the coefficients in the balanced equation, convert mols C2H2 to mols H2O (HOH).
Now convert mols H2O to g. g = mols H2O x molar mass H2O = ?