Which of the following substances is a strong electrolyte?

• A. NH_3 (aq)
• B. CH_3COOH (aq)
• C. NaCl (aq)
• D. C_6H_{12}O_6 (aq)

Answer: (C)

Verified step by step guidance

1. Understand what a strong electrolyte is: a substance that completely dissociates into ions when dissolved in water, resulting in a solution that conducts electricity very well.
2. Analyze each substance given: NH_3 (aq) is ammonia, a weak base that partially ionizes in water; CH_3COOH (aq) is acetic acid, a weak acid that partially ionizes; NaCl (aq) is sodium chloride, an ionic compound that fully dissociates into Na^+ and Cl^- ions; C_6H_{12}O_6 (aq) is glucose, a molecular compound that does not ionize in water.
3. Recall that strong electrolytes are typically soluble ionic compounds or strong acids/bases that dissociate completely, while weak electrolytes only partially ionize and nonelectrolytes do not ionize at all.
4. Identify NaCl (aq) as the strong electrolyte because it is an ionic salt that dissociates completely into ions in aqueous solution.
5. Conclude that the other substances are either weak electrolytes or nonelectrolytes based on their partial or no ionization in water.