When water is electrolysed it breaks down into hydrogen and oxygen:
2h2o
2h₂ + o2
what mass of hydrogen is produced by the electrolysis of 6g of water?

0.67 g

Explanation:

Data given

water (H₂O) = 6 g

Mass of Hydrogen = ?

Electrolysis of water

                    2H₂O > 2H₂ + O₂

Solution:

In hydrolysis of water the water molecule splits in hydrogen and oxygen

                     2H₂O > 2H₂ + O₂

So,  we know from reaction that 2 mole of water molecule splits in 2 mole of hydrogen and 1 mole of oxygen

                     2H₂O > 2H₂ + O₂

                     2mol              2 mol

If we represent mol in grams

Then,

Molar mass of water (H₂O) = 2(1) + 16

Molar mass of water (H₂O) = 18 g/mol

                    2H₂O        > 2H₂ + O₂

             2 mol (18 g/mol)         2 mol (2 g/mol)

                      2H₂O  > 2H₂ + O₂

                        36 g              4 g

It is obvious from the reaction that 36 g of water give 4 g of hydrogen on electrolysis.

Then how many grams of hydrogen will produce if 6 grams of water electrolyzed

apply unity formula

                      36 g of H₂O ≅ 4 g of H₂

                       6 g of H₂O ≅ x g of H₂

By doing cross multiplication

                         g of H₂ = 4 x 6 / 36

                          g of H₂ = 0.67 g

0.67 g of hydrogen will produce if 6 grams of water is electrolyzed

if you're asking what comes out, it's steam.