Question

Calcium hydride reacts with water to form hydrogen gas and calcium hydroxide. How many grams of calcium hydride are needed to generate 53.5 liters of hydrogen gas if the pressure is 814 torr at 21*C.

Answer 1

The Equation is CaH2(s)+2H2O(l)-->Ca(OH)2(aq)+2H2(g)

so,

moles of H2 generated = PV / RT

R = 62.363 L Torr K−1 mol−1

number of moles = 814 * 53.5 / 62.363 * 293

= 2.38 moles

looking at the equation these came from 2.38 /2 moles of CaH2 or 1.19 moles

Molar mass of CaH2 is 42.0943 g/mol

so mass of CaH2 = 1.19 X 42.1 = 50.01g