Question 18:
A substance that can act either as a base or an acid is called:
Amphoteric Substance Acid Base
A substance capable of acting as both acid and base is amphoteric, though the closest option uses “ampholyte.” The correct choice is (A).
Correct Answer
(A) Ampholyte
Ampholytes (or amphoteric substances) have both acidic and basic groups, allowing them to donate or accept protons based on conditions, like amino acids or water.
Key Concept
Amphoteric behavior follows from Greek “amphoteros” (both). Water reacts with HCl as a base (H₂O + HCl → H₃O⁺ + Cl⁻) but with NH₃ as an acid (H₂O + NH₃ → NH₄⁺ + OH⁻).
Option Analysis
-
(A) Ampholyte: Correct; synonym for amphoteric compound, common in biochemistry for zwitterions.
-
(B) Analyte: Incorrect; substance being measured in analysis, unrelated to acid-base duality.
-
(C) Antagonist: Incorrect; blocks receptor activity in pharmacology, not acid-base chemistry.
-
(D) Aptamer: Incorrect; synthetic nucleic acid binding specific targets, used in biotech.
| Option | Term | Definition | Status |
|---|---|---|---|
| A | Ampholyte | Acts as acid or base | Correct |
| B | Analyte | Substance under analysis | Wrong |
| C | Antagonist | Receptor blocker | Wrong |
| D | Aptamer | Nucleic acid ligand | Wrong |
Exam Preparation Tips
Note: “Ampholyte” specifically denotes amphoteric electrolytes; amino acids exemplify via -COOH (acidic) and -NH₂ (basic) groups. Distinguish from purely acidic/basic substances.
