The Question is from neet-chemistry classification-of-elements nitrogen-family-group-15, and it was created by the author P SRAVAN KUMAR

Question

Which of the following statements regarding the oxoacids of phosphorus is INCORRECT?

P SRAVAN KUMAR · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: Oxoacids of Phosphorus and their basicity
 **Related Topics**: Acid-base chemistry, structural formulas of oxoacids
 **Prerequisites**: Understanding of basicity (number of ionizable protons), Lewis structures, and the concept of oxidation states.
## SOLUTION PATHWAY
**Given Information**:
    Four statements regarding the basicity of different oxoacids of phosphorus.
**Method & Steps**:
 1. Analyze each statement individually to determine its correctness.
  Reasoning: We need to determine the number of ionizable protons in each oxoacid.
  Formula/Rule: The number of ionizable protons (H atoms bonded to oxygen) determines the basicity.
 2. Draw the Lewis structures of each oxoacid to identify ionizable protons.
  Working:
        * $H_3PO_4$ (Orthophosphoric acid): Has three ionizable protons (OH groups).  It's tribasic.
        * $H_3PO_2$ (Hypophosphorous acid):  Has only one ionizable proton (OH group). Two H atoms are directly bonded to P. It is monobasic.
        * $H_4P_2O_7$ (Pyrophosphoric acid): Has four ionizable protons (four OH groups). It's tetrabasic.
        * $H_3PO_3$ (Phosphorous acid): Has two ionizable protons (two OH groups). One H atom is directly bonded to P. It is dibasic.
  Key Point:  Protons directly attached to the phosphorus atom are not ionizable in these acids. 
 3. Identify the incorrect statement.
  Result: Statement B, stating that $H_3PO_2$ is a tribasic acid, is incorrect. It is actually monobasic.
  Verification: The Lewis structures confirm the number of ionizable protons.
 ## OPTION ANALYSIS
A ✓: $H_3PO_4$ is indeed tribasic because it has three ionizable protons.
B :x: $H_3PO_2$ is monobasic, not tribasic, as only one proton is ionizable.
 C ✓: $H_4P_2O_7$ is indeed tetrabasic because it has four ionizable protons.
D ✓: $H_3PO_3$ is dibasic, as it has two ionizable protons.
 ## LEARNING AIDS
 **Common Mistakes**:
  1. Incorrectly counting all hydrogen atoms as ionizable:  Only those bonded to oxygen are ionizable in these oxoacids.
  2. Not drawing proper Lewis structures to visualize the bonding and identify ionizable protons.
 **Quick Tips**:
  1. Focus on the number of OH groups in the oxoacid structure to quickly determine basicity.
  2. Remember that H atoms directly bonded to the central phosphorus atom are not acidic (not ionizable).

P SRAVAN KUMAR · Answer

Orthophosphoric acid ($H_3PO_4$) is a tribasic acid.

P SRAVAN KUMAR · Answer

The correct Option is "Hypophosphorous acid ($H_3PO_2$) is a tribasic acid."

P SRAVAN KUMAR · Answer

Pyrophosphoric acid ($H_4P_2O_7$) is a tetrabasic acid.

P SRAVAN KUMAR · Answer

Phosphorous acid ($H_3PO_3$) is a dibasic acid.

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