Molar mass:
CaH2 = 42.094 g/mol
H2 = 2.01 g/mol
CaH2 + 2 H2O = Ca(OH)2 + 2 H2
42.094 g ------------------------------ 2 x 2.01 g
?? ( mass of CaH2) --------------- 4.550 g
4.550 x 42.094 / 2 x 2.01 =
191.5277 / 4.02 => 47.64 g of CaH2
hope this helps!
