For each of the following substances, select the alcohol which you would expect to be the best solvent. (a) I2 CH3OH CH3CH2OH CH3CH2CH2OH CH3CH2CH2CH2OH CH3CH2CH2CH2CH2OH (b) NaCl CH3OH CH3CH2OH CH3CH2CH2OH CH3CH2CH2CH2OH CH3CH2CH2CH2CH2OH (c) CH3CH2CH2CH2CH3 CH3OH CH3CH2OH CH3CH2CH2OH CH3CH2CH2CH2OH CH3CH2CH2CH2CH2OH

(a) CH₃CH₂CH₂CH₂CH₂OH

(b) CH₃OH

(c) CH₃CH₂CH₂CH₂CH₂OH

Explanation:

In alcohols, the - OH group is responsible for the polarity. The longer the non-polar hydrocarbon chain, the less polar is the compound.

Regarding solubility, we will consider the general rule "like dissolves like", meaning polar is soluble in polar and non-polar is soluble in non-polar.

(a) I₂ is non-polar, so it will be more soluble in the least polar solvent, which is pentanol (CH₃CH₂CH₂CH₂CH₂OH).

(b) NaCl is an ionic compound, that is, there is a big difference in electronegativity between the atoms. Then, it will be soluble in the most polar alcohol, methanol (CH₃OH).

(c) Pentane (CH₃CH₂CH₂CH₂CH₃) is non-polar, so it will be more soluble in the least polar solvent, which is pentanol (CH₃CH₂CH₂CH₂CH₂OH).