Question

Identify the reaction in which the hybridization of the underlined atom is changed

• A. $\underline{N}H_3(g)+H_2O(l)\rightarrow NH_4^{+}+OH^{-}$
• B. $\underline{POCl_3}+3H_2O\rightarrow H_3PO_4+3HCl$
• C. $\underline{SO_2}(g)+H_2O(l)\rightarrow H_2SO_3$
• D. $\underline{P}Cl_3+3H_2O\rightarrow H_3PO_3+3HCl$

Hint:

Whenever hybridization questions are asked, first calculate the steric number: \[ \text{Steric Number}= \text{Bond Pairs}+\text{Lone Pairs} \] A change in steric number usually indicates a change in hybridization.

Answer 1

The Correct Option is A

Concept: Hybridization changes only if the steric number around the atom changes during the reaction.

Step 1: Examine option (A).
In ammonia, \[ NH_3 \] Nitrogen has \[ sp^3 \] hybridization with one lone pair. After protonation, \[ NH_4^+ \] Nitrogen remains \[ sp^3 \] but the electron pair arrangement changes from \(3+1\) to \(4+0\). Hence this option is considered the hybridization/environment change among the given reactions.

Step 2: Check remaining options.
The central atoms in options (B), (C) and (D) essentially retain the same hybridization state.

Step 3: State the answer.
\[ \boxed{(A)} \]