Question

Consider the following reaction: 
A + alkali → B (Major Product)
If B is an oxoacid of phosphorus with no P-H bond, then A is

• A. White P₄
• B. Red P₄
• C. P₂O₃
• D. H₃PO₃

Answer 1

The Correct Option is B

The given chemical reaction involves a species A reacting with an alkali to produce B, which is identified as an oxoacid of phosphorus that does not contain any P-H bonds. This requires us to determine the identity of A from the given options.

Let's examine each of the options in the context of this reaction:

• White P₄: White phosphorus typically forms PCl₃ or other derivatives when reacted with alkalis, rather than a phosphorus oxoacid with no P-H bonds.
• Red P₄: Red phosphorus can lead to the formation of orthophosphoric acid (H₃PO₄) upon reaction with alkali.
• P₂O₃: This is an incorrect representation as P₂O₃ is not a stable compound for reacting to form an oxoacid.
• H₃PO₃: This is phosphorous acid with P-H bonds, and therefore cannot be the correct choice as B does not contain P-H bonds.

By eliminating the other options, red phosphorus (Red P₄) is the plausible choice for A. Red phosphorus reacts with alkalis, such as NaOH, to ultimately produce orthophosphoric acid (H₃PO₄):

Overall Reaction:

P_4 + 3 NaOH + 3 H_2O \rightarrow PH_3 + 3 NaH_2PO_2

Further Reaction (Simplified):

P_4 + 20 NaOH + 8 H_2O \rightarrow 8 NaH_2PO_4 + 10 H_2

Finally leading to orthophosphoric acid:

NaH_2PO_4 + H_2O \rightarrow H_3PO_4 + NaOH

Hence, the major product B, being orthophosphoric acid (H₃PO₄), confirms choice A as red phosphorus. Since orthophosphoric acid is an oxoacid of phosphorus with no P-H bonds, the correct answer is Red P₄.