A chemist observes a cubic microscopic region (analysis box) of an aqueous solution…
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A chemist observes a cubic microscopic region (analysis box) of an aqueous solution that contains exactly the following particles:
• 6 Na⁺ ions and 6 Cl⁻ ions (originating from dissolved NaCl)
• 4 glucose molecules (C₆H₁₂O₆)
• 180 H₂O molecules
All particles are fully dispersed and the volume of the analysis box is the same as that used in all subsequent parts.
Answer the following questions about the particle-level structure of this solution.
(a) Describe the orientation and relative arrangement of the surrounding water molecules in the primary solvation shell of (i) a Na⁺ ion, (ii) a Cl⁻ ion, and (iii) a glucose molecule.
(b) Explain, with reference to electrolyte versus nonelectrolyte behavior, why exactly 12 solute particles (rather than 10) are present in the analysis box even though the formula unit counts for NaCl and glucose are equal (6 ions from NaCl counted individually, 4 molecules of glucose).
(c) If the chemist were to compare an otherwise identical analysis box that instead contained 8 glucose molecules (with the NaCl amount unchanged), describe qualitatively how the measured electrical conductivity of that second sample would differ from the original and justify your answer based on particle counts.