# How many Grams of of Hydrogen will be relased when water reacts with 10 of Ca,and 10 gram of CaH2.The answers are 0.5 gram of H2 and b 0.95 gram of H2.

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When water reacts with calcium, the equation of the chemical reaction is: Ca + 2H2O --> Ca(OH)2 + H2

For every mole of calcium in the reacts we have one mole of hydrogen being released. The molar mass of calcium is 40, 10 g of calcium is 1/4 of a mole. Therefore 1/4 mole of hydrogen is produced. As the molar mass of hydrogen is 2, the mass of hydrogen released is 2*(1/4) = 1/2 = 0.5 g

When water reacts with CaH2, the equation of the chemical reaction is: CaH2 + 2H2O --> Ca(OH)2 + 2H2

For every mole of CaH2 we have two moles of H2 released. The molar mass of CaH2 is 42, 10 g is 10/42 mole. The number of moles of H2 released is 2*(10/42). The mass of 10/21 mole of hydrogen is 20/21 = 0.95 g