Question

The compound(s) with P–H bond(s) is(are):

• A. \( \text{H}_3\text{PO}_4 \)
• B. \( \text{H}_3\text{PO}_3 \)
• C. \( \text{H}_4\text{P}_2\text{O}_7 \)
• D. \( \text{H}_3\text{PO}_2 \)

Hint:

In oxoacids of phosphorus: \begin{itemize} \item H atoms attached to O → acidic \item H atoms directly attached to P → non-ionizable, contribute to P–H bonds \end{itemize}

Answer 1

The Correct Option is B, D

To determine whether a compound contains P–H bonds, we must examine its molecular structure. The presence of P–H bonds is identified by the number and nature of hydrogen atoms directly bonded to phosphorus rather than those attached via O–H groups. Let us analyze each option: (A) \( \text{H}_3\text{PO}_4 \) — Orthophosphoric acid: Structure: \[ \text{O} = \text{P}(OH)_3 \] - All three hydrogen atoms are bonded to oxygen (i.e., O–H), none to phosphorus directly. \[ \Rightarrow No P–H bond \] (B) \( \text{H}_3\text{PO}_3 \) — Phosphorous acid: Structure: \[ \text{HO}–\text{P}(=O)–\text{OH} \quad \text{and one direct P–H bond} \] - Two hydrogens via O–H, one directly attached to phosphorus. \[ \Rightarrow 1 P–H bond \quad \text{✅} \] (C) \( \text{H}_4\text{P}_2\text{O}_7 \) — Pyrophosphoric acid: Structure: \[ \text{Two P atoms, each connected through oxygen bridge, and all H atoms via O–H} \] - No hydrogen is directly attached to phosphorus. \[ \Rightarrow No P–H bond \] (D) \( \text{H}_3\text{PO}_2 \) — Hypophosphorous acid: Structure: \[ \text{H–P}(=O)(OH) \] - One O–H and two direct P–H bonds. \[ \Rightarrow 2 P–H bonds \quad \text{✅} \] % Summary:

• (A): No P–H
• (B): 1 P–H
• (C): No P–H
• (D): 2 P–H