Problem 32 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The number of \(\mathrm{P}-\mathrm{O}-\mathrm{P}\) bonds in cyclic metaphosphoric acid is [2000S] (a) zero (b) two (c) three (d) four

Step-by-Step Solution

Answer

Three P-O-P bonds are present in cyclic metaphosphoric acid.

Step 1: Understand Metaphosphoric Acid

Cyclic metaphosphoric acid is a condensed form of phosphoric acid, characterized by its ring structure where phosphorus and oxygen atoms alternate forming P-O bonds. Let's denote metaphosphoric acid as \(\left(\mathrm{HPO}_3\right)_n\), where `n` is the number of repeating units.

Step 2: Recognize the Structure of Cyclic Metaphosphoric Acid

In cyclic metaphosphoric acid, each phosphorus (P) atom forms two P-O bonds (with adjacent phosphate groups), and each oxygen (O) acts as a bridge between two phosphorus atoms. Hence, the structure includes continuing P-O-P bonds throughout the ring.

Step 3: Determine the Number of P-O-P Bonds

For a cyclic structure of metaphosphoric acid, the number of P-O-P bonds formed is equal to the number of phosphorus atoms in the cycle. With three PO3 groups forming the cyclic compound \((\mathrm{HPO}_3)_3\), there will be three P-O-P bonds present.

Step 4: Identify the Answer

Based on the analysis, cyclic metaphosphoric acid with three repeating units \((\mathrm{HPO}_3)_3\) has three P-O-P bonds. Thus, the correct number of such bonds is directly related to the option given in the question.

Key Concepts

P-O-P Bonds

P-O-P bonds are a type of bond found in certain phosphorus-containing compounds, particularly in cyclic metaphosphoric acids. These bonds form when a phosphorus atom shares oxygen atoms with adjacent phosphorus atoms. In a cyclic metaphosphoric acid, the structure is such that each phosphorus atom is bonded to an adjacent one through oxygen bridges, creating a continuous loop or ring.
Understanding P-O-P bonds is crucial in analyzing the structure of condensed phosphoric acids. These bonds contribute to the unique chemical properties of the compound, as they not only form closed rings but also influence the stability and reactivity of the molecule.

• P-O-P bonds create a ring structure in cyclic metaphosphoric acid.
• Each phosphorus atom is bonded to two oxygen atoms that bridge to adjacent phosphorus atoms.
• In a structure such as \(\left(\mathrm{HPO}_3\right)_3\), there are typically three P-O-P bonds.

This specific ring structure with P-O-P bonds is what distinguishes cyclic metaphosphoric acid from other types of phosphoric acids.

Phosphorus-Oxygen Cycle

The phosphorus-oxygen cycle refers to the repeated bonding pattern of phosphorus and oxygen atoms in phosphorus-containing structures. In cyclic metaphosphoric acid, this cycle occurs as phosphorus and oxygen atoms alternate, forming a repeating pattern.
This structural feature is important because it creates the cyclic nature of the acid. Each phosphorus atom acts as a vertex within the ring, and alternating oxygen atoms maintain the integrity and continuity of the cycle through strong P-O bonds.

• The cycle involves continuous alternation of P and O atoms.
• The repeating unit in cyclic metaphosphoric acids is \(\mathrm{HPO}_3\).
• Ensures the compound maintains a symmetrical and stable structure.

The phosphorus-oxygen cycle’s repeating bonds create intriguing properties, making cyclic metaphosphoric acids useful in different chemical applications.

Condensed Phosphoric Acid

Condensed phosphoric acids, like cyclic metaphosphoric acid, are formed when phosphoric acid units link together, eliminating water in a process called condensation. This results in the creation of cyclic structures with P-O-P bonds.
Condensed phosphoric acids show unique structural characteristics compared to their non-condensed counterparts. The linking of multiple phosphoric acid units creates intriguing chemical dynamics, significantly different from simple phosphoric acid.

• These acids form through a dehydration reaction, removing water.
• The cyclic structure results from specific bonding patterns between phosphorus and oxygen.
• The condensed form gives it distinct properties such as higher stability and particular chemical reactivity.

The cyclic and condensed nature of these acids influences their behavior in chemical reactions and their applications in various industries, from manufacturing to pharmaceuticals.