Question

why is the amount of gas collected in one of the test tubes amount collected in the other ? name this gas

Answer 1

hydrogen gas collected during the electrolysis of water is double in the to the amount of of oxygen
2H2O=2H2+O2
on balancing

Answer 2

Hydrogen gas collected at the cathode will be double the volume of oxygen gas collected at the anode.This is because, according to the law of constant proportions,one molecule of water contains hydrogen and oxygen in the ratio 2:1 .Therefore,H2 collected will be double the volume of O2.