What would the total mass of the products of a reaction in which 10g of water decomposes into the elements hydrogen and oxygen?
The equation representing the chemical decomposition of water into hydrogen and oxygen is:
`2H_2O -> 2H_2 + O_2`
When n moles of water decomposes 2n moles of hydrogen and n moles of oxygen is formed. The molar mass of water is 18. The mass of hydrogen in 10 g of water is `(10/18)*2 = 10/9` g. The mass of oxygen in 10 g of water is `(10/18)*16 = 80/9` g.
The mass of hydrogen released in the decomposition of 10 g water is `10/9` g and the mass of oxygen released is `80/9` g. The total mass of the two is `10/9 + 80/9 = 90/9` = 10 g.
This complies with the law of conversation of mass that states that the total mass of the reactants is equal to the total mass of the products in a chemical reaction.