Choose the member of each set that has the higher solubility in water. Briefly, explain your answer.

a) CH₃CH₂CH₃ or CH₃OCH₃

Answer:

To begin to answer this question we need to determine the most important intermolecular attractive force for both of these compounds. To assign the IMAF we need to know if the compound is polar or nonpolar.

So first determine the polarity of CH₃CH₂CH₃ or CH₃OCH₃

The Lewis structure for CH₃CH₂CH₃ is;

Another view of this structure uses a ball-and-stick model;

The central atoms have no lone pairs and all of the terminal atoms are the same so the type of IMAF are dispersion forces for propane.

The Lewis structure for CH₃OCH₃ is;

Another view of this structure uses a ball-and-stick model;

The central oxygen atom has two lone pairs so the type of IMAF are dipole-dipole and dispersion forces for propane.

Now we can reach a conclusion which of the two compounds is more soluble.

Dimethyl ether, CH₃OCH₃, is more soluble in water than propane, CH₃CH₂CH₃. Since dimethyl ether is polar it will be more soluble in water (a polar solvent) compared to propane a nonpolar substance.

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