The weight of hydrogen gas obtained from 42g of CaH2 by treatment with water is ..... gm.
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Solution
CaH2+2H2O→Ca(OH)2+2H2↑ The molar mass of CaH2=40+2=42 g/mol. The number of moles of CaH2=42g42g/mol=1mol 1 mole of CaH2 will liberate 2 moles of H2 The molar mass of H2=2 g/mol The mass of H2 gas obtained =2g/mol×1mol=2g