Question

list the following substances in order of increasing boiling points: bacl₂, h₂, co, hf
a) bacl₂ < hf < co < h₂
b) h₂ < co < hf < bacl₂
c) h₂ < co < bacl₂ < hf
d) hf < bacl₂ < co < h₂

Explanation:

Step1: Identify types of substances

$H_2$ and $CO$ are non - polar and polar covalent molecules respectively. $HF$ is a covalent molecule with hydrogen bonding. $BaCl_2$ is an ionic compound.

Step2: Consider intermolecular forces

$H_2$ has weak London dispersion forces. $CO$ has dipole - dipole forces in addition to London dispersion forces. $HF$ has strong hydrogen bonding along with London dispersion and dipole - dipole forces. Ionic compounds like $BaCl_2$ have strong ionic bonds.

Step3: Rank boiling points

The strength of intermolecular/intramolecular forces is: London dispersion forces in $H_2$ < dipole - dipole forces in $CO$ < hydrogen bonding in $HF$ < ionic bonds in $BaCl_2$. So the order of increasing boiling points is $H_2

Answer:

B. $H_2