# How do I rank the following compounds from lowest to highest boiling point: calcium carbonate, methane, methanol (CH₄O), dimethyl ether (CH₃OCH₃)?

May 17, 2014

The order of boiling points is: ${\text{CH"_4 < "CH"_3"OCH"_3 < "CH"_4"O" < "CaCO}}_{3}$

#### Explanation:

The order of strengths of intermolecular forces is: $\text{ion-ion > H-bonding > dipole-dipole > London dispersion}$.

Compounds with stronger intermolecular forces have higher boiling points.

The strongest intermolecular force in each of the compounds is:

${\text{CaCO}}_{3}$ — ion-ion attractions.
${\text{CH}}_{4}$ — London dispersion forces
$\text{CH"_3"OH}$ — hydrogen bonding
${\text{CH"_3"OCH}}_{3}$ — dipole-dipole attractions

${\text{CaCO}}_{3}$ is an ionic compound. It has the highest boiling points

Next comes methanol, $\text{CH"_4"O}$ or $\text{CH"_3"OH}$.

Methanol has strong hydrogen bonds. It will have the next highest boiling point. Dimethyl ether, ${\text{CH"_3"OCH}}_{3}$, is a polar molecule.

The $\text{C-O}$ bond dipoles reinforce each other, so the molecule has a dipole moment.

Dipole-dipole forces are not as strong as hydrogen bonds, so dimethyl ether has a lower boiling point than methanol does.

Finally, the $\text{C-H}$ bonds in methane are nonpolar, so the molecule is also nonpolar.

It has only weak London dispersion forces, ${\text{CH}}_{4}$, has the lowest boiling point.

The order of boiling points is:

${\text{CH"_4 < "CH"_3"OCH"_3 < "CH"_4"O" < "CaCO}}_{3}$

Here's a good video on ordering compounds according to their intermolecular forces and boiling points.