CaC2 + 2 H2O = C2H2 + Ca(OH)2
moles CaC2 = 485 g/64.1 g/mol=7.57
moles H2O = 2 x 7.57 =15.1
mass H2O = 15.1 mol x 18.02 g/mol=272.8 g
moles C2H2 = 23.6 /26.038 g/mol=0.906
moles CaC2 = 0.906
mass CaC2 = 0.906 x 64.1 =58.1 g
moles Ca(OH)2 = 55.3 / 74.092 =0.760
moles H2O = 2 x 0.760 =1.52
mass water = 18.02 x 1.52 =27.4 g
