Piyush is a student of class 10. His teacher was teaching the type of chemical reactions in the class. Piyush was aksed to carry out the reaction of electrolysis of water in the laboratory. Piyush set up the complete apparatus for the electrolysis of water. He took pure water (distilled water) to carry out this reaction. When Piyush passed electric current through this water for a considerable time even then no chemical reaction took place. Piyush told this problem to his classmate Arjun. Arjun thought over the problem and asked Piyush to add a little of a certain substance into pure water before passing electric current through it. When electric current was passed thorugh water after adding a little of this substance then a chemical reaction took place to form two gases `X` and `Y`. The volume of gas `X` collected over one of the electrodes was `8mL` whreas the volume of gas `Y` collected over the other electrode was `16mL`
(a) Why no chemical reaction took place when electric current was passed thorugh pure water?
(b) What substance was added in little quantity to pure water before passing electric current again?
(c) How did the addition of little of this substance help in the electrolysis of water?
(d) What is gas `X`? Over which electrode is it collected?
(e) What is gas `Y`? Over which electrode is it collected?
(f) What type of chemical reaction is demonstrated by this experiment ? Why?
(g) What values are displayed by Arjun in this episode?

Explanation

(a) because pure water (or distilled water) is a non conductor of electricity.
(b) Sulphuric acid.
(c) Sulphuric acid is an electrolyte. The addition of a little of sulphuric acid made water a good conductor of electricity. (The water containing a little of sulphuric acid is called acidified water).
(d) The gas `X` is oxygen. It is collected over the positive electrode (called anode).
(e) The gas `Y` is hydrogen. It is collected over the negative electrode (called cathode).
(f) This experiment shows a decomposition reaction. In his decomposition reaction water decompose into two constituents : oxygen and hydrogen.
(g) The values displayed by Arjun in this episode are: (i) Awareness (or knowledge) that pure water is a non-conductor of electricity which can be made a god conductor by adding a little of dilute sulphuric acid, and (ii) Helping nature.