Increase the electrical conductivity of the solution.
Explanation
Electrolysis is the process of decomposing a chemical compound by passing an electric current through it. For this process to occur, the liquid medium (electrolyte) must be capable of conducting electricity, which requires the presence of free-moving ions.
Analysis:
- Conductivity of Pure Water: Pure or distilled water is a very poor conductor of electricity because it ionizes to a negligible extent. It lacks sufficient free ions ($H^+$ and $OH^-$) to carry an electric current effectively.
- Role of Dilute Sulphuric Acid: When a small amount of dilute sulphuric acid ($H_2SO_4$) is added to water, it dissociates completely into hydrogen ions ($H^+$) and sulphate ions ($SO_4^{2-}$). These ions act as charge carriers, significantly increasing the electrical conductivity of the solution. This allows the current to flow through the circuit, enabling the decomposition of water into hydrogen and oxygen.
Evaluation of Other Options:
- Lower the temperature of the solution. Incorrect: The addition of acid does not lower the temperature of the solution.
- Catalyze the formation of gas bubbles. Incorrect: While the presence of ions allows the reaction to proceed, the primary function is to establish conductivity, not to act as a surface catalyst for bubble formation.
- Prevent the corrosion of the electrodes. Incorrect: Acids are generally corrosive. The addition of acid makes the solution more corrosive, necessitating the use of inert electrodes (such as platinum) rather than preventing corrosion.
Key Takeaway: Pure water is an electrical insulator. To perform electrolysis, an electrolyte (such as an acid, base, or salt) must be added to provide free ions and increase the electrical conductivity of the solution.