Problem 125 - A Complete Resource Book in Chemistry for JEE Main

Question

In the following questions two statements (Assertion) (A) and Reason (R) are given. Mark (a) If both \(\mathrm{A}\) and \(\mathrm{R}\) are correct and \(\mathrm{R}\) is the correct explanation of \(\mathrm{A}\). (b) If both \(\mathrm{A}\) and \(\mathrm{R}\) are correct but \(\mathrm{R}\) is not the correct expalnation of \(\mathrm{A}\). (c) A is true but \(\mathrm{R}\) is false. (d) A is false but \(R\) is true. (e) \(\mathrm{A}\) and \(\mathrm{R}\) both are false. Assertion: Fluorine forms only one oxoacid, HOF because. Reason: Fluorine has small size and high electronegativity.

Step-by-Step Solution

Answer

(a) Both A and R are correct and R is the correct explanation of A.

Step 1: Understanding the Assertion

The assertion states that fluorine forms only one oxoacid, HOF. This implies that the unique characteristics of fluorine lead to it forming a limited number of oxoacids. Analyze if this characteristic holds true based on chemistry knowledge.

Step 2: Analyzing the Reason

The reason provided is that fluorine forms only one oxoacid due to its small size and high electronegativity. Consider how these properties might influence fluorine's ability to form additional oxoacids.

Step 3: Evaluating the Relationship Between A and R

Since fluorine's high electronegativity makes it the strongest oxidizing agent, it often prevents it from forming oxoacids with multiple oxygens. Its small size contributes to its high electronegativity and the stability of HOF. Therefore, both the assertion and reason are correct, and the reason acts as an appropriate explanation for the assertion.

Key Concepts

Oxoacids of Fluorine

Fluorine, an intriguing element situated at the top of the halogen group in the periodic table, is known for its unique properties. Among its compounds, oxoacids are particularly interesting for their reactivity and rarity. In fact, fluorine forms only one notable oxoacid: hypofluorous acid, represented as HOF. The reason behind this singular manifestation is rooted in fluorine's intrinsic characteristics.

• Structure and Stability: HOF is formed when fluorine is bound to an oxygen atom, which in turn is connected to a hydrogen atom. This simple structure is stable due to fluorine's high affinity for electrons, which binds the oxygen tightly to the fluorine atom, maintaining the integrity of the molecule.
• Influence of Electronegativity: The high electronegativity of fluorine means it strongly attracts electrons, stabilizing the bond with oxygen and making it challenging to share bonds with multiple oxygen atoms, thereby inhibiting the formation of additional oxoacids.

The rarity of fluorine oxoacids in contrast to other halogens like chlorine, which forms several, highlights fluorine's distinctive chemistry.

Electronegativity

Electronegativity is a key concept in understanding why fluorine behaves the way it does in chemical reactions. It is essentially a measure of how strongly an atom attracts electrons towards itself when bonded with another atom. Fluorine is the most electronegative element in the periodic table. This attribute influences not only its reactive nature but also other properties.

• Bonding Characteristics: Due to its high electronegativity, fluorine tends to form polar bonds as it attracts electrons more than most other elements. In compounds like HOF, this results in a strong oxygen-fluorine bond where electrons are unequally shared.
• Effect on Chemistry: High electronegativity makes fluorine a very reactive element, capable of forming stable compounds with almost all elements. However, it also restricts fluorine from forming multiple bonded structures with oxygen, unlike less electronegative halogens.

The value of electronegativity helps chemists predict behaviors and outcomes in chemical reactions involving fluorine and other elements.

Oxidizing Agents in Chemistry

In chemistry, oxidizing agents are substances that accept electrons during a chemical reaction, facilitating the oxidation of other substances. Fluorine, due to its high electronegativity and reactivity, is considered the most powerful oxidizing agent. This makes it crucial in various chemical processes, often determining the direction and outcome of reactions.

• Role in Reactions: As an oxidizing agent, fluorine can easily gain an electron to form the fluoride ion, transforming substances it interacts with. Its ability to act as a strong oxidizer is linked to its capacity to draw electrons happening due to its high electronegativity.
• Versatility and Applications: The strong oxidizing nature of fluorine finds applications in industrial oxidations, organic chemistry, and even pharmaceuticals where controlled oxidation is required.

Its efficiency as an oxidizing agent not only influences its chemical interactions but also limits its ability to form compounds with elements that do not readily lose electrons, such as oxygen, explaining its limited oxoacid formation.