Problem 157 - A Complete Resource Book in Chemistry for JEE Main

Question

Number of P-O bonds in \(\mathrm{P}_{4} \mathrm{O}_{10}\) is (a) 17 (b) 16 (c) 15 (d) 6

Step-by-Step Solution

Answer

The number of P-O bonds in \(\mathrm{P}_{4} \mathrm{O}_{10}\) is 16.

Step 1: Understanding the Structure of \(\mathrm{P}_{4} \mathrm{O}_{10}\)

The molecule \(\mathrm{P}_{4} \mathrm{O}_{10}\) is composed of four phosphorus atoms and ten oxygen atoms. To find out the number of P-O bonds, we should first understand how these atoms are arranged structurally. \(\mathrm{P}_{4} \mathrm{O}_{10}\) generally forms a cage-like structure where each phosphorus atom forms bonds with oxygen atoms, and the structure is made up of \(\mathrm{P-O-P}\) bridges and \(\mathrm{P=O}\) double bonds.

Step 2: Counting P-O Bonds in the Structure

In the structure of \(\mathrm{P}_{4} \mathrm{O}_{10}\), each phosphorus atom is bonded to four oxygen atoms in total. This includes one terminal \(\mathrm{P=O}\) double bond and three bridging \(\mathrm{P-O-P}\) bonds. Since there are four phosphorus atoms, we calculate the total number of P-O bonds: - 4 terminal \(\mathrm{P=O}\) double bonds contribute 4 bonds.- Each P forms 3 bridges with O, giving a total of since these are shared between neighboring P atoms, contributing 6 \((3 \times 4 / 2))\) bridges.Together this sums up to 16 P-O bonds.

Key Concepts

Molecular Structure

Phosphorus pentoxide, represented as \(\mathrm{P}_{4} \mathrm{O}_{10}\), has a unique and intricate molecular structure that resembles a cage. This structure consists of phosphorus and oxygen atoms arranged in such a way that maximizes stability. Each of the four phosphorus atoms is centrally located and bonded to oxygen atoms, creating a three-dimensional architecture. The arrangement of atoms forms two tetrahedra joined together, sharing a common vertex. By visualizing this formation, one can understand how phosphorus pentoxide achieves its high stability and efficiency in chemical reactions. Familiarity with this molecular geometry is crucial to comprehend the behavior of \(\mathrm{P}_{4} \mathrm{O}_{10}\) in various chemical contexts.

Chemical Bonds

Chemical bonding in \(\mathrm{P}_{4} \mathrm{O}_{10}\) involves both single and double bonds that connect phosphorus and oxygen atoms. Through these bonds, the molecule gains structural integrity and chemical properties.

• Single Bonds: The molecule features single bonds in the form of \(\mathrm{P-O-P}\) bridges. These single bonds connect phosphorus atoms via oxygen, contributing significantly to the molecule's structural framework.
• Double Bonds: Each phosphorus atom also forms a double bond \(\mathrm{P=O}\) with an oxygen atom. These double bonds are crucial for stability, as they strengthen the linkage of atoms, making \(\mathrm{P}_{4} \mathrm{O}_{10}\) sturdy.

Understanding these bonds is essential for grasping how \(\mathrm{P}_{4} \mathrm{O}_{10}\) interacts with other substances and its role in chemical reactions.

Covalent Bonding

Covalent bonding is the backbone of the \(\mathrm{P}_{4} \mathrm{O}_{10}\) molecule's stability and structure. In covalent bonds, atoms share electrons to fill their outer shells, achieving a lower energy state and increased stability. Within \(\mathrm{P}_{4} \mathrm{O}_{10}\), covalent bonds facilitate the sharing of electrons between phosphorus and oxygen atoms. Each phosphorus atom forms covalent bonds with oxygen atoms, either in double bonds (\(\mathrm{P=O}\)) or single bridges (\(\mathrm{P-O-P}\)).To visualize these interactions:

• The terminal \(\mathrm{P=O}\) bond involves the sharing of two pairs of electrons, leading to a double bond.
• The \(\mathrm{P-O-P}\) bonds result from the sharing of one pair of electrons between each phosphorus and oxygen as part of the single bond network.

Covalent bonding here plays a critical role in the molecule's ability to form stable linkages, ensuring resistance to decomposition under standard conditions.

Chemical Nomenclature

Chemical nomenclature is the systematic naming of chemical compounds and is critical for clear communication in science. The name 'phosphorus pentoxide' refers specifically to its composition and molecular formula, \(\mathrm{P}_{4} \mathrm{O}_{10}\).

• Phosphorus: The prefix indicates the presence of phosphorus atoms.
• Pentoxide: The term reflects the presence of ten oxygen atoms, with 'pent' referring to the element oxygen appearing five times as \(\mathrm{O}_{5}\) in each provide or indicate a double \(\mathrm{O}_{2}\).

This system of nomenclature aids in the identification and differentiation of phosphorus pentoxide from other phosphorus-oxygen compounds, ensuring precision in chemical literature and discussions.