An unknown substance is found to be a solid at room temperature, will not dissolve in oil but will in water, and conducts electricity. What compound is the unknown substance, KCl, Alcohol, or Chlorine gas?
The Correct answer and Explanation is:
Based on the characteristics provided, the unknown substance is most likely KCl (potassium chloride).
Explanation
- Physical State: The substance is described as a solid at room temperature. Potassium chloride is a solid crystalline compound at room temperature, whereas alcohol (like ethanol) is a liquid at room temperature, and chlorine gas (Cl₂) is, of course, a gas.
- Solubility: The unknown substance does not dissolve in oil but does dissolve in water. KCl is an ionic compound that readily dissolves in polar solvents like water due to the strong electrostatic interactions between the ions (K⁺ and Cl⁻) and the polar water molecules. In contrast, alcohols typically have moderate solubility in both polar and non-polar solvents, and chlorine gas does not dissolve in water significantly.
- Electrical Conductivity: The substance is able to conduct electricity. Ionic compounds like KCl, when dissolved in water, dissociate into their constituent ions. These free-moving ions allow the solution to conduct electricity effectively. In contrast, alcohols do not conduct electricity as they do not dissociate into ions in solution. Chlorine gas is also a poor conductor of electricity since it is a molecular gas and does not produce free ions.
Conclusion
Based on these three criteria—being a solid at room temperature, solubility in water (not in oil), and ability to conduct electricity—the unknown substance is KCl (potassium chloride). The properties of KCl align perfectly with the descriptions given, confirming it as the correct answer.