The number of calcium hydride that are needed to form 4.850 g of hydrogen gas =101.85 grams
calculation
write the equation for decomposition of CaH2
that is CaH2→ Ca +H2
find the moles of H2 produced = 4.850/2 =2.425 moles
by use of mole ratio between CaH2:H2 which is 1:1 the moles of CaH2 is also 2.425 moles
mass of CaH2 is therefore = moles x molar mass
= 2.425 moles x 42 g/mol= 101.85 grams
