How many grams of calcium hydride are needed to form 4.850 g of hydrogen gas? express your answer using four significant figures?

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