Question:
Assertion (A): H\(_2\)SO\(_4\) acts as a base in the presence of perchloric acid.
Reason (R): Ortho phosphoric acid is a weaker acid than H\(_2\)SO\(_4\). (Assume equal concentration in all cases)
Assertion (A): H\(_2\)SO\(_4\) acts as a base in the presence of perchloric acid.
Reason (R): Ortho phosphoric acid is a weaker acid than H\(_2\)SO\(_4\). (Assume equal concentration in all cases)
Reason (R): Ortho phosphoric acid is a weaker acid than H\(_2\)SO\(_4\). (Assume equal concentration in all cases)
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A species can act as base even if it is an acid, when placed in presence of a stronger acid.
Updated On: Jun 20, 2026
- Both A and R are correct and R is the correct explanation of A
- Both A and R are wrong
- A is wrong but R is correct
- Both A and R are correct, but R is not the correct explanation of A
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The Correct Option is D
Solution and Explanation
Step 1: Analyze Assertion (A).
H\(_2\)SO\(_4\) is a strong acid, but in presence of an even stronger acid like HClO\(_4\) (perchloric acid), it can accept a proton due to relative acid strength comparison. Thus, H\(_2\)SO\(_4\) can behave as a base in superacidic medium.
Step 2: Analyze Reason (R).
Ortho phosphoric acid (H\(_3\)PO\(_4\)) is indeed a weaker acid than H\(_2\)SO\(_4\). This is correct based on acidity order: \[ H_3PO_4 < H_2SO_4 < HClO_4 \]
Step 3: Check validity of both statements.
Both Assertion and Reason are individually correct statements based on acid strength concepts in acid–base chemistry.
Step 4: Check logical connection.
However, the reason talks about relative acidity of phosphoric acid and sulfuric acid, which is unrelated to why H\(_2\)SO\(_4\) acts as a base in presence of perchloric acid.
Step 5: Identify correct relationship.
The assertion depends on superacid behavior and proton donation/acceptance concept, not on comparison with phosphoric acid. Hence R does not explain A.
Step 6: Final conclusion.
Both statements are correct, but the reasoning is not the correct explanation of the assertion.
Final Answer: \[ \boxed{(4)} \]
H\(_2\)SO\(_4\) is a strong acid, but in presence of an even stronger acid like HClO\(_4\) (perchloric acid), it can accept a proton due to relative acid strength comparison. Thus, H\(_2\)SO\(_4\) can behave as a base in superacidic medium.
Step 2: Analyze Reason (R).
Ortho phosphoric acid (H\(_3\)PO\(_4\)) is indeed a weaker acid than H\(_2\)SO\(_4\). This is correct based on acidity order: \[ H_3PO_4 < H_2SO_4 < HClO_4 \]
Step 3: Check validity of both statements.
Both Assertion and Reason are individually correct statements based on acid strength concepts in acid–base chemistry.
Step 4: Check logical connection.
However, the reason talks about relative acidity of phosphoric acid and sulfuric acid, which is unrelated to why H\(_2\)SO\(_4\) acts as a base in presence of perchloric acid.
Step 5: Identify correct relationship.
The assertion depends on superacid behavior and proton donation/acceptance concept, not on comparison with phosphoric acid. Hence R does not explain A.
Step 6: Final conclusion.
Both statements are correct, but the reasoning is not the correct explanation of the assertion.
Final Answer: \[ \boxed{(4)} \]
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