Final answer:
Acetic acid (CH₃COOH) is the weak electrolyte when dissolved in water, as it does not dissociate completely like the other substances listed, making it partially ionize in solution.
Step-by-step explanation:
The question asks which of the following compounds is a weak electrolyte when dissolved in water:
- Sodium chloride (NaCl)
- Hydrochloric acid (HCl)
- Acetic acid (CH₃COOH)
- Potassium hydroxide (KOH)
Sodium chloride (NaCl) is a strong electrolyte because it dissociates completely in water into sodium and chloride ions. Hydrochloric acid (HCl) is also a strong electrolyte as it exists as hydronium and chloride ions in solution. Potassium hydroxide (KOH) is a strong base and therefore a strong electrolyte as well. The compound that is a weak electrolyte is acetic acid (CH₃COOH), as it partially dissociates in water, releasing a smaller concentration of ions compared to strong electrolytes.