text: acetylene gas is produced from calcium carbide and water.if 32 g of calcium carbide are consumed, how many g ? grams of water are needed? thank you everybody..... the balanced reaction is: cac2 + 2h2o ---> c2h2 + ca(oh)2  the molar mass of cac2 is 64 g/mol so you are starting with 0.5 moles of calcium carbide.  since water reactions with cac2 is a 1:2 ratio, you will need twice as much water, or 1.0 moles of water = 18 grams of water.