Question

In which case hydrogen bond will not be observed
(a) H₃O₂⁻
(b) H₂O
(c) H₅O₂⁺
(d) H₃O⁺

Answer 1

The correct answer is H3O+.

• in hydrogen bond a dative bond is present.

• with the decrease in electronegativity , formation of H-bond decrease.

Answer 2

Hydrogen Bond will not be observed in

d) H₃O⁺

Hydrogen bonding is a special type of dipole-dipole attraction between molecules, not a covalent bond to a hydrogen atom. It results from the attractive force between a hydrogen atom covalently bonded to a very electronegative atom such as a N, O, or F atom and another very electronegative atom.

When we see the definition of hydrogen bonding above and also the structure of all the options, we get to see

a) In H₃O₂⁻ ,we have a $OH^{-}$ attached to a water molecule, where in one Oxygen atom has negative charge and the other is as normal as in a water, i.e. with two lone pairs leading to high electronegativity.

b) H₂O - A simple water molecule with one  Oxygen highly electronegative.

c) H₅O₂⁺ - A water molecule attached to H₃O⁺, with one Oxygen having positive charge and one normal highly electronegative Oxygen.

d)H₃O⁺ - A water molecule with a H+ ions attached, leading to positive charge on Oxygen i.e no Highly electronegative Oxygen atom in the molecule.

  Therefore, there is no Electronegative atom in d)H₃O⁺ leading to no Hydrogen bonding in this case.