B. E. Douglas, D. H. McDaniel, J. J. Alexander, Concepts and Models of Inorganic Chemistry, 3rd edition, John Wiley & Sons, New York, 1994, page 250.

Problem 5.23

Suggest a solvent, other than H2O, for studies of ionic substances. Explain the reasons.

Answer:

To dissolve an ionic substance the large lattice energy must be overcome by solvation. This requires a solvent with a large dielectric constant and/or high polarity. Solvents like acetonitrile or methanol are polar but the dielectric constants are still only moderate (37 for acetonitrile and 33 for methanol). Better choices (other than for safety reasons) might be liquid HF ( = 84), formamide ( = 111), or N-methylacetamide ( = 179).