Which of the following is amphoteric substance?

Correct answer: C. H₂O

  • A. Na₂O
  • B. H₂CO₃
  • C. H₂O
  • D. NH₄OH

Explanation

An amphoteric substance has the ability to act as both an acid and a base. Water (H₂O) is a classic example of an amphoteric substance because it can donate a proton, forming hydroxide ions (OH⁻), or accept a proton, forming hydronium ions (H₃O⁺). Therefore, it can behave as either an acid or a base depending on the reaction conditions. In contrast, Na₂O is a basic oxide, H₂CO₃ is primarily an acid, and NH₄OH is a weak base, none of which exhibit the dual functionality required to be considered amphoteric.

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About Acids, Bases and Salts

Acid and base behaviour is explained through the Bronsted-Lowry transfer of protons and the Lewis donation or acceptance of electron pairs. The topic includes pH, pOH, ionisation and water equilibrium, plus salt formation and hydrolysis, where a salt solution may become acidic, basic or neutral.

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