• Take a plastic mug. Drill two holes at its base and fill rubber stoppers in these holes. Insert carbon electrode in these rubber stoppers as shown in Fig.
• Connect these electrodes to a 6 volt battery.
• Fill the mug with water such that the electrodes are immersed. Add a few drops of dilute sulphuric acid to the water.
•Take two test tubes filled with water and invert there over the two carbon electrodes. Switch on the current and leave the apparatus undisturbed for some time.
• You will observe the formation of bubbles at both the electrodes. These bubbles displace water in the test tubes.
Is the volume of the gas collected the same in both the test tubes ?

Explanation

No, volume of gas in both the test tubes is not the same. Once the test tubes are filled with the respective gases, remove them carefully.
Test these gases one by one by bringing a burning candle close to the mouth of the test tubes.
CAUTION : This step must be performed carefully by he teacher.