Problem 138 - A Complete Resource Book in Chemistry for JEE Main

Question

Which are correct statements for \(\mathrm{XeF}_{2}\) ? (a) it oxidizes \(\mathrm{Cl}^{-}\)and \(\mathrm{I}^{-}\)to \(\mathrm{Cl}_{2}\) and \(\mathrm{I}_{2}\) respectively (b) it has linear structure (c) it cannot act as \(\mathrm{F}\) - donor (d) it is hydrolyzed rapidly in aqueous solution of a base (a) 1,2 and 4 (b) 1,3 and 4 (c) 2,3 and 4 (d) 3 and 4 only

Step-by-Step Solution

Answer

Correct statements for XeF2 are 2 and 4, aligning with option (c).

Step 1: Analyze Statement (a)

XeF2 is a strong oxidizing agent, which can oxidize I- to I2 but not Cl- to Cl2, because chlorine is more electronegative and does not get oxidized by XeF2. Therefore, statement (a) is incorrect.

Step 2: Analyze Statement (b)

The molecular geometry of XeF2 is linear. This is because it has two bonding pairs and three lone pairs of electrons, with the shape dictated by the VSEPR theory (AX2E3 type), resulting in a linear structure. Therefore, statement (b) is correct.

Step 3: Analyze Statement (c)

XeF2 can act as a fluoride donor under specific conditions. It can release F- ions in certain chemical reactions, so it is incorrect to say that it cannot act as an F- donor. Therefore, statement (c) is incorrect.

Step 4: Analyze Statement (d)

XeF2 is hydrolyzed rapidly in aqueous solutions, especially basic solutions. It reacts with water to produce xenon gas, hydrofluoric acid, and oxygen. This makes statement (d) correct.

Step 5: Determine Correct Combination of Statements

The correct statements from our analysis are (b) and (d). Comparing these conclusions to the given options, only option (c), which lists 2, 3, and 4, is consistent with our finds with statements (b) and (d) alone.

Key Concepts

Oxidizing Agent

An oxidizing agent is a substance that has the ability to oxidize other substances, meaning it accepts electrons from them.
In the process, the oxidizing agent itself gets reduced. XeF2 is recognized as a strong oxidizing agent, particularly adept at oxidizing iodide ions (I⁻) to iodine (\(I_{2}\)).
However, it does not oxidize chloride ions (\(Cl^{-}\)) to chlorine (\(Cl_{2}\)) due to chlorine's greater electronegativity and stability compared to iodine.
This difference in chemical behavior is important for understanding how XeF2 interacts with other substances. It's crucial in determining the correct answer for the exercise, where it was falsely suggested that XeF2 could oxidize both I⁻ and Cl⁻ ions.

VSEPR Theory

The VSEPR theory, which stands for Valence Shell Electron Pair Repulsion theory, is a model used to predict the geometry of individual molecules based on electron-pair electrostatic repulsion.
The fundamental idea is that pairs of electrons around a central atom will arrange themselves as far apart as possible to minimize repulsion.
In the case of XeF2, the molecule contains two bonding pairs and three lone pairs of electrons surrounding the xenon atom.
According to VSEPR theory, this geometry corresponds to an AX2E3 type, resulting in a linear molecular structure.

• Bonding pairs: The fluorine atoms bonded to xenon
• Lone pairs: The non-bonding pairs around xenon

Therefore, the theory correctly predicts XeF2 as having a linear shape, which aligns with the provided solution stating that XeF2 is indeed linear.

Molecular Geometry

Molecular geometry is the three-dimensional arrangement of atoms within a molecule.
In XeF2, this particular geometry is determined by the electron pair repulsions following VSEPR theory.
With two bonded atoms (fluorine) and three lone pairs around xenon, the electrons arrange themselves to minimize repulsion, forming a linear shape.
This linear geometry is typical for molecules with an AX2E3 electronic configuration.

• Linear shape: Atoms are positioned 180 degrees apart
• Effect of lone pairs: Despite their influence, the lone pairs themselves are not part of the visible geometry

Understanding molecular geometry is crucial as it impacts molecular properties and reactions. It is fundamental to various applications, including predicting molecule behavior in reactions.

Fluoride Donor

A fluoride donor is any molecule that can donate fluoride ions (F⁻) in a chemical reaction.
XeF2 can act as a fluoride donor under certain conditions.
In particular scenarios, it can release F⁻ ions, which can then participate in further chemical reactions, transforming XeF2 into a valuable reagent in coordination chemistry.
This unexpected feature can surprise those who assume XeF2 is solely a fluoride acceptor without examining specific conditions.

• Reactivity: Depends on the surrounding chemical environment
• Applications: Used in various synthetic processes for its fluorine donating ability

The ability of XeF2 to donate fluoride ions challenges certain misconceptions and requires a deeper understanding of its reactivity in different environments. As the exercise solution clarifies, dismissing XeF2 as a non-donor is incorrect.