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Explain the role of the conjugate acid/base pair, H₂PO₄⁻/HPO₄²⁻, in maintaining the pH of living cells - HSC - SSCE Chemistry - Question 25 - 2011 - Paper 1
Question 25
Explain the role of the conjugate acid/base pair, H₂PO₄⁻/HPO₄²⁻, in maintaining the pH of living cells. Include chemical equations in your answer.
Worked Solution & Example Answer:Explain the role of the conjugate acid/base pair, H₂PO₄⁻/HPO₄²⁻, in maintaining the pH of living cells - HSC - SSCE Chemistry - Question 25 - 2011 - Paper 1
Step 1
State the role of H₂PO₄⁻/HPO₄²⁻ as a buffer system in the cell
Answer
The conjugate acid/base pair H₂PO₄⁻/HPO₄²⁻ plays a crucial role in maintaining the pH of living cells by acting as a buffer system. Buffers resist changes in pH when small amounts of acids or bases are added. In the cellular environment, this pair can donate protons (H⁺) when the pH increases (becoming less acidic) and can accept protons when the pH decreases (becoming more acidic), thus stabilizing the pH.
Step 2
Provide two correct equations
Answer
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When the pH of the solution decreases (adding acid):
This reaction shows HPO₄²⁻ acting as a base, accepting a proton to form H₂PO₄⁻.
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When the pH of the solution increases (adding base):
In this reaction, H₂PO₄⁻ acts as an acid, donating a proton to form HPO₄²⁻.