To solve this problem, we must first assume that CaH2 acts like an ideal gas so that we can use the ideal gas equation:
P V = n R T
where,
P = pressure = 825 torr
V = volume = 145 L
n = number of moles = unknown
R = universal gas constant = 62.36367 L Torr /mol K
T = absolute temperature = 22°C = 295.15 K
Finding for n:
n = P V / R T
n = (825 torr) (145 L) / (62.36367 L Torr /mol K * 295.15 K)
n = 6.5 mol
Molar mass of CaH2 is 42.1 g/mol, therefore the mass is:
mass CaH2 = (6.5 mol) (42.1 g/mol)
mass CaH2 = 273.65 g
