Question

what mass of CaH2 is produced at the end
of 5g of Ca with excess H2?

Answer 1

CaH2 --> Ca + H2↑
1) n(Ca) = 5g : 40g/mol = 0,125mol
2) n(CaH2) = n(Ca) = 0,125mol
3) m(CaH2) = 0,125mol * 42g/mol = 5,25g