# Is a molecule of hydrogen chloride (HCI) polar or nonpolar?

Mar 2, 2017

$\text{Hydrogen chloride}$ is a highly POLAR molecule........

#### Explanation:

Because chlorine is MORE electronegative than hydrogen, chlorine in the $H C l$ molecule polarizes electron density towards itself. We could represent this as:

""^(+delta)H-Cl^(delta-).

The $H - C l$ molecule is thus a polar covalent molecule, in which the electronegative chlorine atom strongly polarizes electron density. In water, the polarization is so pronounced that the $H - C l$ bond completely ionizes:

""^(+delta)H-Cl^(delta-) + H_2O rarr H_3O^+ + Cl^-.

And thus solutions of $H C l \left(a q\right)$ are stoichiometric in ${H}_{3} {O}^{+}$, $\text{hydronium ion}$, and $C {l}^{-}$, the chloride ion. In the gas phase, however, we have the $H - C l$ molecule, which has a normal boiling point of $- 85.0$ ""^@C. Sometimes, you will see gas cylinders of $H C l$, the which requires special regulators and special precautions and apparatus to handle. Why so......??

So the moral? As a gas, $H C l$ is molecular; as a solution in water, $H C l$ ionizes. Gaseous ammonia is the same sort of molecule, however, ammonia acts as a weak base in water.