CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Two sealed syringes, A and B, each contain an aqueous solution of potassium nitrate at 25 °C. Syringe A holds a total solution volume of 2.0 mL; syringe B holds 8.0 mL. A chemist injects both solutions, without loss of liquid, into two identical 1.0 mL observation cells so that the volumes inside the cells are the same. After transfer, the following particle counts (water molecules omitted) are obtained inside each 1.0 mL cell.
From syringe A → 36 K⁺ ions and 36 NO₃⁻ ions
From syringe B → 14 K⁺ ions and 14 NO₃⁻ ions
(a) Determine which observation cell now contains the more concentrated solution. Support your answer with quantitative reasoning based on the particle counts provided.
(b) Before transfer, which syringe (A or B) originally held the more concentrated potassium nitrate solution? Justify your answer using both the syringe volumes and the post-transfer particle data.
(c) Suppose the chemist wishes to create a solution exactly half as concentrated as the one now present in the more concentrated cell. Describe the change in total number of solute particles that must be present in the same 1.0 mL cell volume to achieve that concentration, and explain how this relates to dilution at the particle level.