Problem 12 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Good reducing nature of \(\mathrm{H}_{3} \mathrm{PO}_{2}\) is attributed to the presence of: [Main Jan. 9, 2019 (II)] (a) Two \(\mathrm{P}-\mathrm{OH}\) bonds (b) One \(\mathrm{P}-\mathrm{H}\) bond (c) Two \(\mathrm{P}-\mathrm{H}\) bonds (d) One P - OH bond

Step-by-Step Solution

Answer

The presence of two \( \mathrm{P-H} \) bonds attributes to the good reducing nature of \( \mathrm{H}_3\mathrm{PO}_2 \).

Step 1: Understanding the Compound Structure

The structure of hypophosphorous acid, or \( \mathrm{H}_3\mathrm{PO}_2 \), consists of one phosphorus atom bonded to two hydrogen atoms directly (\( \mathrm{P-H} \)), one hydroxyl group (\( \mathrm{P-OH} \)), and one double-bonded oxygen (\( \mathrm{P=O} \)).

Step 2: Identifying Reducing Elements

The good reducing nature of \( \mathrm{H}_3\mathrm{PO}_2 \) is associated mainly with the presence of \( \mathrm{P-H} \) bonds, because hydrogen atoms attached to phosphorus can be donated to other substances, reducing them.

Step 3: Counting the Reducing Bonds

In the \( \mathrm{H}_3\mathrm{PO}_2 \) molecule, there are two \( \mathrm{P-H} \) bonds. The presence of these two \( \mathrm{P-H} \) bonds is crucial for its reducing nature.

Step 4: Conclusion on Reducing Nature

Therefore, the good reducing nature of \( \mathrm{H}_3\mathrm{PO}_2 \) is attributed to the presence of two \( \mathrm{P-H} \) bonds, which distinguishes it from other phosphorous acids with fewer \( \mathrm{P-H} \) bonds.

Key Concepts

Reducing nature

The reducing nature, or the ability of a substance to donate electrons or hydrogen, is an important chemical property. Hypophosphorous acid, with the chemical formula \( \mathrm{H}_3\mathrm{PO}_2 \), is particularly known for its pronounced reducing nature. This stems from its capability to easily donate hydrogen atoms. It plays a vital role in redox reactions, where it acts as a reducing agent. This means it helps other substances gain electrons, thereby reducing them. Hypophosphorous acid, specifically, is efficient in this role due to the presence of its phosphorus-hydrogen bonds. This property makes it very useful in fields requiring reduction processes, such as in plating industries where it helps in metal electroplating.

To sum up, the reducing nature of \( \mathrm{H}_3\mathrm{PO}_2 \) is predominantly due to its unique ability to donate hydrogen and electrons, simplifying chemical synthesis in industrial applications.

Phosphorus-hydrogen bonds

Phosphorus-hydrogen bonds are critical in understanding the chemistry of hypophosphorous acid. In \( \mathrm{H}_3\mathrm{PO}_2 \), these bonds are key contributors to its reducing abilities. There are specifically two \( \mathrm{P-H} \) bonds present.

These \( \mathrm{P-H} \) bonds are directly responsible for the acid's ability to act as a reducing agent. Here's how they contribute:

• These bonds become a "donor," providing electrons and hydrogen during chemical reactions.
• They are relatively more active compared to other types of chemical bonds due to the attraction between phosphorus and hydrogen.
• The energy required to break these \( \mathrm{P-H} \) bonds is lower, making it easier for hypophosphorous acid to "donate" these atoms.

The robustness of these phosphorus-hydrogen bonds plays a crucial role in its application, especially when modifying other substance's oxidation states.

Thus, understanding these bonds provides a clear explanation of why \( \mathrm{H}_3\mathrm{PO}_2 \) is favored as a reducing agent in various chemical processes.

Chemical structure

The chemical structure of hypophosphorous acid is essential to explore to understand its properties fully. Represented as \( \mathrm{H}_3\mathrm{PO}_2 \), its unique make-up defines its chemical behavior. Here is a breakdown of its structural components:

• One phosphorus atom forms the core of the molecule.
• It is bonded to two hydrogen atoms through \( \mathrm{P-H} \) bonds.
• It has a single hydroxyl group, \( \mathrm{P-OH} \), which is quite characteristic of many acids.
• Additionally, there is one double-bonded oxygen, \( \mathrm{P=O} \), in the compound.

The structure is pivotal because it gives rise to the two critical \( \mathrm{P-H} \) bonds. These bonds directly correlate with the molecule's ability to act as a reducing agent. The chemical structure also determines the stability and reactivity of \( \mathrm{H}_3\mathrm{PO}_2 \) in various environments. This structure allows it to participate effectively in many industrial and laboratory reactions, serving various chemical and practical applications.

Overall, the chemical structure of \( \mathrm{H}_3\mathrm{PO}_2 \) explains much of its behavior and utility in reducing contexts.