Why is the amount of gas collected in one of the test tubes in text book Activity 1.7 (i.e., electrolysis of water) double of the amount collected in the other? Name this gas.

In Activity 1.7, water is electrolyzed to give H₂ gas at one electrode and O₂ gas at the other electrode.

Thus two molecules of water on electrolysis give two molecules of hydrogen gas and one molecule of oxygen gas or in other words, the amount of hydrogen gas collected would be double that of oxygen gas.