CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Four equal-volume boxes (W, X, Y, and Z) each depict an aqueous solution that contains only one type of solute. Water molecules are omitted. The verbal descriptions of solute particles in each box are as follows:
Box W: 12 methanol (CH₃OH) molecules
Box X: 6 sodium ions and 6 fluoride ions
Box Y: 6 calcium ions and 12 chloride ions
Box Z: 9 urea (NH₂CONH₂) molecules
(a) Rank the four boxes from highest to lowest concentration based on the number of dissolved particles actually present. Write your ranking in the form "highest > > > lowest."
(b) Provide a clear rationale for why Box Y has a different position in your ranking than Box X, even though both boxes contain the same total number of formula units of an ionic compound.
(c) Suppose one wishes to compare the relative concentrations of solute matter (in moles of compound, not individual particles) across the boxes. Explain how your ranking in part (a) would change, if at all, and justify your answer.