Are nonelectrolytes always nonpolar?

...Nonelectrolytes are substances that dissolve in water but contain no ions so they do not conduct electricity. However, if the nonelectrolytes contain no ions they would be nonpolar and therefore would not dissolve in water. So how can nonelectrolytes dissolve in water? An example would be sugar. Is it nonpolar? Yet it dissolves in water. Is this an exception to the "like dissolves like " rule?
A High School Chemistry Teacher 1/17/99

A compound need not "contain ions" to be polar. Any compound with molecules with centers of positive and negative charge that don't coincide is polar. If the molecule is not symmetrical, and contains atoms with a wide range of electronegativities, it's likely to be polar.

Table sugar (sucrose) is a polar nonelectrolyte. Sucrose is quite soluble because its molecules bristle with water-accessible OH groups, which can form strong hydrogen bonds with water. So sugar is not an exception to the "like dissolves like" rule of thumb.

Nonelectrolytes can be either polar or nonpolar. Nonpolar nonelectrolytes can be sparingly soluble in water, especially if they contain small electronegative atoms that water can hydrogen-bond to. Examples are O₂ and CO₂. If these nonpolar substances didn't dissolve in water, life as we know it would not be possible!

Author: Fred Senese senese@antoine.frostburg.edu

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