Distilled water
Explanation
The ability of a liquid to conduct electricity depends on the presence of free-moving charged particles, known as ions. Liquids that dissociate into ions (electrolytes) allow electric current to flow, while those that do not produce free ions act as electrical insulators.
Analysis of Options:
- A solution of caustic soda (A solution of caustic soda): Incorrect.
Caustic soda (Sodium Hydroxide, NaOH) is a strong base. When dissolved in water, it dissociates completely into sodium ions (Na+) and hydroxide ions (OH-). These free ions facilitate the flow of electric current, making the solution a conductor. - A solution of common salt (A solution of common salt): Incorrect.
Common salt (Sodium Chloride, NaCl) is an ionic compound. In an aqueous solution, it dissociates into sodium ions (Na+) and chloride ions (Cl-). The movement of these ions enables the solution to conduct electricity. - Distilled water (Distilled water): Correct.
Distilled water is chemically pure H2O free from dissolved salts and minerals. It has a negligible degree of ionization (producing very few H+ and OH- ions). Due to the absence of sufficient free charge carriers, it does not conduct electricity and acts as an insulator. - Dilute hydrochloric acid (Dilute hydrochloric acid): Incorrect.
Hydrochloric acid (HCl) is a strong acid. In a dilute solution, it ionizes readily to release hydrogen ions (H+) and chloride ions (Cl-), making the liquid a good conductor of electricity.
Key Takeaway:
Pure water is a poor conductor of electricity due to the lack of free ions. Conductivity in liquids is primarily caused by the presence of dissolved electrolytes (acids, bases, or salts) that dissociate into mobile ions.