Question

rank the following three structures a, b and c, below, in order of their expected boiling points, based on what you expect to be the most important intermolecular forces relevant to each. (lowest) b < c < a (highest) (lowest) b < a < c (highest) (lowest) a < c < b (highest) (lowest) a < b < c (highest)

Explanation:

Step1: Identify intermolecular forces

Molecule A has hydrogen - bonding due to the - OH group, which is a strong intermolecular force. Molecules B and C have only London dispersion forces (LDFs) as they lack hydrogen - bonding groups. LDFs depend on molar mass and molecular surface area.

Step2: Compare molar mass and surface area for B and C

Molecules B and C have similar structures. But B has a slightly larger molar mass and more surface area due to the extra methyl group compared to C. Larger molar mass and surface area lead to stronger LDFs.

Step3: Rank boiling points

Stronger intermolecular forces mean higher boiling points. A has the strongest intermolecular forces (hydrogen - bonding), B has stronger LDFs than C, and C has the weakest LDFs among the three. So the order of boiling points is C < B < A.

Answer:

A. (lowest) C < B < A (highest)