In the decomposition of water. How many grams of Hydrogen will be produced by 20g of water?

The equation for the reaction is is 2H2O = 2H2 + O2

Ratio of H to O in water = 2:1

Molar mass of water = 2*1.008 + 15.999 = 18.015

18.015 g gives 2*1.008 hydrogen

20 gives 2 * 1.008 * 20 / 18.015

= 2.24 g hydrogen to the nearest hundredth.