Final answer:
The substance that is an electrolyte among the given options is (a) Na₂SO₄ (sodium sulfate) because it dissociates into ions when dissolved in water.
Step-by-step explanation:
The question asks which of the following substances is an electrolyte: (a) Na₂SO₄, (b) C₁₂H₂₂O₁₁, (c) CH₃CH₂OH, and (d) PF₆. By definition, an electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water, because it ionizes. The substance that fits this description is sodium sulfate (Na₂SO₄), as it dissociates into ions in solution:
- Na₂SO₄ (sodium sulfate) - Dissolves in water to form Na+ and SO₄²− ions, making it an electrolyte.
- C₁₂H₂₂O₁₁ (sucrose) - A non-electrolyte, as it does not dissociate into ions in solution.
- CH₃CH₂OH (ethanol) - Also a non-electrolyte since it does not ionize in solution.
- PF₆ (phosphorus hexafluoride) - A non-electrolyte because it does not produce ions in solution.
Thus, the correct answer is (a) Na₂SO₄, an electrolyte.