Question

The incorrect statements among the following is:

• A. PH\(_3\) shows lower proton affinity than NH\(_3\).
• B. PF\(_3\) exists but NF\(_5\) does not.
• C. NO\(_2\) can dimerise easily.
• D. SO\(_2\) can act as an oxidizing agent, but not as a reducing agent.

Hint:

When dealing with oxidation and reduction reactions, keep in mind that many compounds can function as both oxidizing and reducing agents depending on the conditions. SO\(_2\) is a classic example of such a compound.

Answer 1

The Correct Option is D

Let's analyze each statement to determine which one is incorrect:

1. PH₃ shows lower proton affinity than NH₃: 

This statement is true. This is because phosphorus (P) has a larger atomic size than nitrogen (N), causing PH₃ to have a weaker tendency to accept a proton compared to NH₃. Thus, PH₃ has a lower proton affinity.

1. PF₃ exists but NF₅ does not:

This statement is valid. PF₃ is a stable compound. However, NF₅ does not exist because nitrogen cannot expand its octet; it only has five valence electrons available for bonding, making it unable to form NF₅.

1. NO₂ can dimerize easily:

This statement is true. Due to the presence of unpaired electrons, NO₂ can dimerize to form N₂O₄ readily.

1. SO₂ can act as an oxidizing agent, but not as a reducing agent:

This statement is incorrect. SO₂ can act as both an oxidizing agent and a reducing agent. It can be reduced to sulfur, and it can also oxidize other substances to form SO₄^2- ions.

The correct answer is: "SO₂ can act as an oxidizing agent, but not as a reducing agent."

Answer 2

Let's evaluate each statement to identify which one is incorrect:

1. PH₃ shows lower proton affinity than NH₃: This statement is correct. Ammonia (NH₃) is more basic than phosphine (PH₃) due to nitrogen's higher electronegativity, resulting in higher proton affinity.
2. PF₃ exists but NF₅ does not: This statement is accurate. Phosphorus readily forms PF₃ with three available valence electrons. Fluorine forms a stable bond with phosphorus, whereas nitrogen has only three valence electrons and cannot form a stable NF₅ compound.
3. NO₂ can dimerise easily: This is true. Nitrogen dioxide (NO₂) has an unpaired electron, which makes it highly reactive and likely to dimerize, forming dinitrogen tetroxide (N₂O₄).
4. SO₂ can act as an oxidizing agent, but not as a reducing agent: This is incorrect. Sulfur dioxide (SO₂) can indeed act as both an oxidizing and a reducing agent depending on the reacting chemical species, due to its ability to undergo both reduction and oxidation reactions.

Therefore, the incorrect statement is: SO₂ can act as an oxidizing agent, but not as a reducing agent.