1. Electrolysis Setup
* Electrolyte: Use a solution like dilute sulfuric acid (H₂SO₄) or potassium hydroxide (KOH) as the electrolyte.
* Electrodes: Use inert electrodes like platinum or graphite.
* Collection Tubes: Two separate test tubes or graduated cylinders, filled with the electrolyte, are inverted over the electrodes.
2. The Process
* Electrolysis: When an electric current is passed through the electrolyte, water molecules split into hydrogen and oxygen gas:
* At the cathode (negative electrode): 2H⁺ + 2e⁻ → H₂ (hydrogen gas is produced)
* At the anode (positive electrode): 2H₂O → O₂ + 4H⁺ + 4e⁻ (oxygen gas is produced)
* Gas Collection: Hydrogen gas will be collected at the cathode, and oxygen gas will be collected at the anode.
3. Separation
* Upward Displacement: The gases are collected by upward displacement of the electrolyte in the inverted tubes. This is because hydrogen and oxygen are less dense than water.
* Separation by Volume: The volume of hydrogen gas collected will be twice the volume of oxygen gas collected (due to the chemical equation for electrolysis).
Important Considerations
* Safety: Electrolysis produces flammable hydrogen gas. Do this experiment only in a well-ventilated area and with appropriate safety precautions.
* Purity: The gases collected may contain traces of the electrolyte. If high purity is required, further purification steps may be necessary.
Summary
The separation of hydrogen and oxygen gas after electrolysis relies on the fact that these gases are produced at different electrodes and have different densities. The process involves collecting the gases by upward displacement and then separating them based on their volume ratio.
