Question

why is the amount of gas collected in one of the test tubes in the above activitiy double of the amount collected in the other? Name the gas.

Answer 1

The gas collected during electrolysis of water at cathode is Hydrogen while the gas collected at anode is Oxygen.

The gas collected at cathode or hydrogen is twice the amount than oxygen because the following decomposition reaction takes place when electricity is passed through water

2H2O —-> 2H2 + O2

From the above decomposition reaction it can be concluded that two molecules of water decompose to give 2 molecules of hydrogen and one molecule of oxygen.

Hence the gas collected at one test tube is double in amount than other.