When 18.02 g of water is decomposed by electrolysis, 16.00 g of oxygen and 2.02 g of hydrogen are formed. according to the law of definite proportions. what mass, in grams, of hydrogen will be formed by the electrolysis of 795 g of water?

According to the law of definite proportions, in a compound the same elements are always present in the same proportions.

On decomposition of 18.02 g of water by electrolysis, 16.0 g of oxygen and 2.02 g of hydrogen are formed.  (given)

Therefore, the ratio of grams of hydrogen to grams of water is:

2.02 g : 18.02 g

So, this ratio can be used to determine the mass of water in 795 g. As:

Hence, of hydrogen will be formed by the electrolysis of 795 g of water.