Question

write activity 1.7 in ncert textbook science class10​

Answer 1

Procedure: The activity asks to electrolyse water using a 6-volt battery and check the volume of gases liberated at anode and cathode. The activity also asks to bring the gas at the flame and see what happens.

Observation:

Gas collected at the cathode (-) is twice that of gas collected at the anode (+).

2. When we bring the flame to the gas collected at the cathode, it burns immediately. While gas obtained at anode does not burn.

Inference: Electricity decomposes water into its component. Hydrogen atoms in water receive an electron from cathode electrode and form hydrogen gas. Similarly, oxygen atoms in water lose electron at the anode and form oxygen gas.

We can explain this with the equation below.

2H2O  ——>  2H2 + O2

Here you can see two molecules of hydrogen gas liberate with one molecule of oxygen. So the volume of hydrogen obtained is double the amount of oxygen.

Note: water is not highly conductive. We use a few drops of sulphuric acid here. It is done to increase the electrical conductivity of water. Instead of sulphuric acid, any other acid like hydrochloric acid or salt like sodium chloride can also work.