During electrolysis of water the amount of gas collected in one of the test tubes is double the amount collected in the other why ?

Explanation

During electrolysis of water, the water molecule decomposes to give hydrogen and oxygen gas. In a water molecule hydrogen and oxygen are present in `2:1` ratio, hence the amount of hydrogen is double the amount of oxygen.
`2H_(2)Ooverset("electric current")(to)2H_(2)+O_(2)`.