4 Most SAQ’s of P-Block Elements Chapter in Inter 2nd Year Chemistry (TS/AP)

4 Marks

SAQ-1 : How does PCl₅ react with the following?
a) Water b) C₂H₅OH c) CH₃COOH d) Ag

Introduction

Phosphorus pentachloride (PCl₅) is known for its high reactivity with various substances, leading to the formation of multiple compounds.

1. Reaction with Water (H₂O)
   • Reaction: $$\textbf{PCl}_5 + 4\textbf{H}_2\textbf{O} \rightarrow \textbf{H}_3\textbf{PO}_4 + 5\textbf{HCl}$$
   • Outcome: PCl₅ reacts with water to produce phosphoric acid (H₃PO₄) and hydrochloric acid (HCl).
2. Reaction with Ethyl Alcohol (C₂H₅OH)
   • Reaction: $$\textbf{PCl}_5 + \textbf{C}_2\textbf{H}_5\textbf{OH} \rightarrow \textbf{C}_2\textbf{H}_5\textbf{Cl} + \textbf{POCl}_3 + \textbf{HCl}$$
   • Outcome: PCl₅ reacts with ethyl alcohol to yield ethyl chloride (C₂H₅Cl), phosphoryl chloride (POCl₃), and hydrochloric acid.
3. Reaction with Acetic Acid (CH₃COOH)
   • Reaction: $$\textbf{PCl}_5 + \textbf{CH}_3\textbf{COOH} \rightarrow \textbf{CH}_3\textbf{COCl} + \textbf{POCl}_3 + \textbf{HCl}$$
   • Outcome: PCl₅ reacts with acetic acid to form acetyl chloride (CH₃COCl), phosphoryl chloride, and hydrochloric acid.
4. Reaction with Silver (Ag)
   • Reaction: $$\textbf{PCl}_5 + 2\textbf{Ag} \rightarrow 2\textbf{AgCl} + \textbf{PCl}_3$$​
   • Outcome: PCl₅ reacts with silver to produce silver chloride (AgCl) and phosphorus trichloride (PCl₃).

Summary

Phosphorus pentachloride (PCl₅) showcases a diverse range of reactions with different substances, leading to the production of various chlorinated compounds, acids, or chloride salts. These reactions highlight PCl₅’s significance in synthesizing chemical compounds, providing valuable insights for students and practitioners in chemistry.

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SAQ-2 : How does PCl₃ react with a) CH₃COOH b) C₂H₅OH c) water

Introduction

Phosphorus trichloride (PCl₃) is a reactive chemical compound utilized in various synthetic reactions to produce chlorinated organic compounds and acids.

1. Reaction with Acetic Acid (CH₃COOH)
   • Reaction: $$3\textbf{CH}_3\textbf{COOH} + \textbf{PCl}_3 \rightarrow 3\textbf{CH}_3\textbf{COCl} + \textbf{H}_3\textbf{PO}_3​$$
   • Outcome: Acetic acid reacts with PCl₃ to form acetyl chloride (CH₃COCl) and phosphorous acid (H₃PO₃), showcasing PCl₃‘s role in acyl halide formation.
2. Reaction with Ethyl Alcohol (C₂H₅OH)
   • Reaction: $$3\textbf{C}_2\textbf{H}_5\textbf{OH} + \textbf{PCl}_3 \rightarrow 3\textbf{C}_2\textbf{H}_5\textbf{Cl} + \textbf{H}_3\textbf{PO}_3$$
   • Outcome: Ethyl alcohol undergoes reaction with PCl₃ resulting in ethyl chloride (C₂H₅Cl) and phosphorous acid, highlighting its applicability in alkyl halide synthesis.
3. Reaction with Water (H₂O)
   • Reaction: $$\textbf{PCl}_3 + 3\textbf{H}_2\textbf{O} \rightarrow \textbf{H}_3\textbf{PO}_3 + 3\textbf{HCl}$$
   • Outcome: PCl₃ reacts violently with water, producing phosphorous acid and hydrochloric acid (HCl), indicating its strong reactivity with water.

Summary

Phosphorus trichloride (PCl₃) is a versatile reagent in chemical synthesis, capable of forming chlorinated organic products and acids upon reaction with acetic acid, ethyl alcohol, and water. These reactions demonstrate PCl₃’s significant role in organic chemistry, particularly in the synthesis of acyl halides and alkyl chlorides, as well as its reactivity with water to produce acids.

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SAQ-3 : What are interhalogen compounds? Give some examples to illustrate the definition. How are they classified?

Introduction

Interhalogen compounds are a distinct class of halogen compounds formed between two different halogens. These compounds are known for their diverse applications, ranging from industrial processes to pharmaceuticals.

Definition of Interhalogen Compounds

Interhalogen compounds are characterized by the chemical bond between two different halogens. Unlike diatomic molecules of the same halogen (e.g., Cl₂), these compounds involve two or more different halogens (e.g., ClF, BrF₃).

Examples of Interhalogen Compounds

1. Chlorine Monofluoride (ClF): A simple binary interhalogen.
2. Bromine Trifluoride (BrF₃): Notable for its powerful oxidizing properties.
3. Iodine Pentafluoride (IF₅): Used in various organic synthesis reactions.
4. Chlorine Trifluoride (ClF₃): Known for its extreme reactivity and use in nuclear reactor fuel processing.

Classification of Interhalogen Compounds

Interhalogen compounds are classified based on the number of atoms involved and their structural arrangement:

1. Binary Interhalogens (XY): Composed of two atoms, such as ClF, BrF. These are the simplest form of interhalogen compounds.
2. Ternary Interhalogens (XY₃): Contain three atoms of two types of halogens, for example, ClF₃, BrF₃. They often have a T-shaped molecular geometry.
3. Quaternary Interhalogens (XY₅): Made up of five atoms, like IF₅, showcasing a square pyramidal structure.
4. Quinary Interhalogens (XY₇): Comprising seven atoms, such as IF₇, which is one of the few known examples and has a pentagonal bipyramidal structure.

Summary

Interhalogen compounds, with their diverse molecular structures and reactivities, are formed by the combination of different halogens. They are classified into binary, ternary, quaternary, and quinary types, based on the number and arrangement of halogen atoms. These compounds are essential in various chemical reactions and industrial applications, highlighting the versatility of halogen chemistry.

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SAQ-4 : a)How are XeO₃ and XeOF₄ prepared?
b)Give the structures of XeO₃ and XeOF₄

Introduction

Xenon, a noble gas, forms compounds like Xenon Trioxide (XeO₃) and Xenon Oxytetrafluoride (XeOF₄), showcasing its ability to participate in chemical reactions despite its inert nature.

Preparation of Xenon Compounds

1. XeO₃ (Xenon Trioxide):
   • Method: XeF₆ reacts with water in a complete hydrolysis reaction.
   • Reaction: $$\textbf{XeF}_6 + 3\textbf{H}_2\textbf{O} \rightarrow \textbf{XeO}_3 + 6\textbf{HF}$$
2. XeOF₄ (Xenon Oxytetrafluoride):
   • Method: XeF₆ undergoes partial hydrolysis with water.
   • Reaction: $$\textbf{XeF}_6 + \textbf{H}_2\textbf{O} \rightarrow \textbf{XeOF}_4 + 2\textbf{HF}$$

Structures of Xenon Compounds

1. XeO₃ (Xenon Trioxide):
   • Hybridization: sp³, with Xe forming three σ bonds with oxygen atoms.
   • Shape: Pyramidal.
   • Bond Angle: Approximately 103°.
2. XeOF₄ (Xenon Oxytetrafluoride):
   • Hybridization: sp³d², involving six hybrid orbitals.
   • Shape: Square pyramidal, due to five bond pairs and one lone pair.
   • Bond Angle: 90° between bonds.

Summary

The compounds XeO₃ and XeOF₄ illustrate xenon’s capacity to form stable molecules with oxygen and fluorine. Their preparation through hydrolysis of XeF₆ and distinct structural characteristics—pyramidal for XeO₃ and square pyramidal for XeOF₄—highlight the versatile nature of xenon beyond its inertness. Understanding these compounds enhances our knowledge of noble gas chemistry and the principles governing molecular geometry.