Which of the following substances is a non-electrolyte?

Step 1: Analyze the question We need the substance that does NOT conduct electricity when dissolved in water or molten, because it does not produce ions.

Step 2: Concept

• Electrolytes break up (ionize or dissociate) into ions in solution or when molten, so they conduct electricity. • Strong electrolytes: strong acids, strong bases, and soluble salts. • Weak electrolytes: weak acids and bases, which ionize only slightly.
• Non-electrolytes are usually covalent compounds that dissolve as whole molecules and form no ions. Examples are sugar (glucose, sucrose), ethanol, urea, and kerosene.

Step 3: Check each option

• A. H₂SO₄: a strong acid. It ionizes fully into H⁺ and SO₄²⁻, so it is a strong electrolyte.
• B. CH₃COOH: ethanoic (acetic) acid. It ionizes only partially into CH₃COO⁻ and H⁺, so it is a weak electrolyte. It still produces some ions, so it is not a non-electrolyte.
• C. C₆H₁₂O₆: glucose. It is a covalent molecule that dissolves in water without forming ions, so it is a non-electrolyte.
• D. NH₄Cl: an ionic salt. It dissociates into NH₄⁺ and Cl⁻, so it is a strong electrolyte.

Step 4: Answer The non-electrolyte is glucose, C₆H₁₂O₆, which is option C.

Exam tip: Sugars and alcohols (glucose, sucrose, ethanol) are the classic non-electrolytes. Remember that "weak electrolyte" is not the same as "non-electrolyte": a weak acid like ethanoic acid still gives a few ions. Also, a compound with the formula pattern C(H₂O)ₙ is usually a sugar, so it is a non-electrolyte.