CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Three molecular solvents—water, acetonitrile, and benzene—are compared as media for dissolving two sodium salts: NaBr and NaPF6. Relevant physical data for the solvents are provided.
Solvent
Dipole moment (D)
Dielectric constant, εr
Water
1.85
78.4
Acetonitrile
3.92
35.9
Benzene
0.00
2.3
(a) Rank the three solvents in order of the expected strength of their interactions with Na+ ions. Provide a brief justification.
(b) Compare the expected strength of solvent interactions with Br− versus PF6− in a polar medium. Include in your discussion the effects of ion size and charge distribution.
(c) For each solvent, predict which of the two salts is more soluble and explain your reasoning, citing evidence from parts (a) and (b).