Kinetic molecular theory?

A sample is collected over water at 760 torr, and the volume is measured as 523 mL. At the temperature of the experiment (23 Celcius), the vapor pressure of water is 21 torr. How many grams of CaC2 would be needed (theoretically) to produce this amount of gas? If the reaction had an actual yield of 78.5%, how much calcium carbide would be required?