22. (a) Define the term amphiprotic - HSC - SSCE Chemistry - Question 22 - 2004 - Paper 1
Question 22
22. (a) Define the term amphiprotic.
(b) Write TWO chemical equations to show that the dihydrogen phosphate ion (H₂PO₄⁻) is amphiprotic.
Worked Solution & Example Answer:22. (a) Define the term amphiprotic - HSC - SSCE Chemistry - Question 22 - 2004 - Paper 1
Step 1
Define the term amphiprotic
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Answer
An amphiprotic substance is one that can act as both an acid and a base. This means it can either donate a proton (H⁺) in a chemical reaction, displaying acidic behavior, or accept a proton, showcasing basic behavior.
Step 2
Write TWO chemical equations to show that the dihydrogen phosphate ion (H₂PO₄⁻) is amphiprotic
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Answer
As an acid:
H₂PO₄⁻ (aq) + H₂O (l) ⇌ HPO₄²⁻ (aq) + H₃O⁺ (aq)
In this reaction, the dihydrogen phosphate ion donates a proton to water, acting as an acid.
As a base:
H₂PO₄⁻ (aq) + H⁺ (aq) ⇌ H₃PO₄ (aq)
Here, the dihydrogen phosphate ion accepts a proton, demonstrating its basic properties.
