Which of the following best describes the effect of increasing the concentration of NaCl in an aqueous solution?

• A. It causes NaCl to precipitate out of the solution.
• B. It reduces the solubility of NaCl in water.
• C. It decreases the boiling point of the solution.
• D. It increases the electrical conductivity of the solution.

Answer: (D)

Verified step by step guidance

1. Understand that NaCl (sodium chloride) is an ionic compound that dissociates completely into Na\textsuperscript{+} and Cl\textsuperscript{-} ions when dissolved in water.
2. Recognize that increasing the concentration of NaCl in an aqueous solution means more ions are present in the solution.
3. Recall that electrical conductivity in a solution depends on the presence and concentration of free ions that can carry electric charge.
4. Therefore, as the concentration of NaCl increases, the number of free ions increases, which enhances the solution's ability to conduct electricity.
5. Note that increasing NaCl concentration does not cause precipitation (unless solubility limits are exceeded), does not reduce solubility, and actually raises the boiling point (boiling point elevation), not decreases it.