Is HCO3- polar or nonpolar? – Polarity of HCO3-

The question is –

Is HCO₃^– polar or nonpolar?

Answer:

⇒ HCO₃^– is polar.

Explanation:

The bicarbonate (HCO₃^–) ion is polar as the unequal dipole moments of C-O (or C=O) and that of the O-H bond does not get canceled equally in the asymmetrical bent molecular shape and geometry.

HCO₃^– consists of two C-O single covalent bonds, one C=O double bond, and an O-H bond.

The C-O single or C=O double bond is polar as it consists of an electronegativity difference of 0.89 units between the covalently bonded carbon (E.N = 2.55) and oxygen (E.N = 3.44) atoms.

In contrast, the O-H bond is strongly polar as an even higher electronegativity difference of 1.24 units exists between an oxygen and a hydrogen (E.N = 2.20) atom.

Oppositely charged poles develop in HCO₃^– as the central C-atom and the terminal H-atom gains partial positive (δ⁺) charges while the three O-atoms gain partial negative (δ^–) charges, respectively.

The shape of the molecular ion w.r.t central C-atom is trigonal planar while that w.r.t the O-H bonded O-atom is bent, angular, or V-shaped.

Two lone pairs of electrons present on the O-H bonded oxygen lead to strong lone pair-lone pair and lone pair-bond pair electronic repulsions, thus distorting the overall molecular shape and geometry.

The net dipole moment of two C-O bonds gets canceled to some extent with the dipole moment of a downwards-pointing C=O bond.

However, the strong dipole moment of an O-H bond stays uncancelled.

The charged electron cloud stays non-uniformly distributed, which leads to an overall polar HCO₃^– ion (net µ > 0).

The C-O single-bonded oxygen atom (at the left) carries a -1 formal charge which is also the charge present on the bicarbonate ion overall.

Also, check –

⇒ How to identify polar or nonpolar compounds?

⇒ Is HCO₃^– an acid or base?