Question

The following compounds have similar molecular weights. which would be expected to have the lowest boiling point?

Answer 1

Answer:

Methane (B) is expected to have the lowest boiling point.

Explanation:

There are to ways of solving this problem.

The first one is considering the physical state of matter that this compounds are found in normal conditions (room temperature):

(A) calcium carbonate  - solid

(B) methane  - gas

(C) methanol (CH₄O)  - liquid

(D) dimethyl ether (CH₃OCH₃) - liquid

Methane is the only gas, therefore it has the lowest boiling point.

The second one is considering the molecular interactions between the molecules of each compound:

(A) calcium carbonate  - it is a salt - eletrostatic interactions between ions - very strong

(B) methane  - non-polar molecule - induced dipole - very weak

(C) methanol (CH₄O)  - polar molecule - dipole-dipole - relatively strong

(D) dimethyl ether (CH₃OCH₃) - liquid - dipole-dipole - relatively strong

The intermolecular interactions in methane are the weakest, therefore it has the lowest boiling point.