Chapter U2.15, Problem 5E

Interpretation Introduction

Interpretation : Whether hexane is soluble in water or not needs to be explained if it is not attracted to a charged wand and it spreads on waxed paper.

Concept Introduction :

There are two classes of molecules; polar and nonpolar. Polar molecules are attracted by a charged wand whereas a nonpolar molecule is not attracted by a charged wand. Examples of polar molecules are water, vinegar, and rubbing alcohol. Examples of nonpolar molecules are mineral oil, hexane, and motor oil.

Answer to Problem 5E

The molecular formula of hexane is C₆H₁₄. It is a nonpolar molecule. So it does not get attracted to a charged wand. Individual hexane molecules are not strongly attracted to each other so they spread out on waxed paper.

A polar molecule will dissolve in water but nonpolar molecules will not dissolve. Non-polar hexane molecules are not attracted to polar water molecules so hexane does not dissolve in water.

Explanation of Solution

A polar molecule is one that has a partial positive charge on one side and a partial negative charge on the other side of the molecule.

Hexane is nonpolar as it does not have partial charges on hydrogen and carbon atoms. So it will not get attracted to the charged wand.

The partial charges on polar molecules not only cause attraction to a charged wand but also cause the attraction between molecules. Hexane is non-polar, so it does not possess a strong intermolecular force of attraction. Hence it spreads on waxed paper.

Being nonpolar, hexane molecules do not get attracted to polar water molecules. So it will not dissolve in water.

Conclusion

Polarity is a molecular property that causes intermolecular attraction which is responsible for many properties of molecules such as solubility in polar solvents, etc.