A student is provided with a reference particle diagram representing a 20.0 mL sample…
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A student is provided with a reference particle diagram representing a 20.0 mL sample of aqueous calcium chloride. In the diagram the student counts 18 chloride ions and 9 calcium ions. The student is asked to prepare, at the particle level, a second diagram showing a solution that is exactly twice as concentrated as the reference solution, while keeping the drawn box volume unchanged.
(a) Specify the exact number of Ca²⁺ ions and Cl⁻ ions that must appear in the new diagram to satisfy the requirement of doubling the concentration. Explain your reasoning.
(b) Justify why adding water molecules to or removing water molecules from the drawing (without changing the box size) would not achieve the required change in concentration.
(c) After completing both diagrams, the student notices that electrical conductivity would differ between the two solutions. Predict which diagram corresponds to the solution with the higher conductivity and explain how the difference in particle counts supports your prediction.