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One litre of an aqueous solution is formed from mixing equal volumes of 0.2 mol L⁻¹ hydrochloric acid (HCl) and 0.2 mol L⁻¹ sodium chloride (NaCl) - HSC - SSCE Chemistry - Question 18 - 2017 - Paper 1
Question 18
One litre of an aqueous solution is formed from mixing equal volumes of 0.2 mol L⁻¹ hydrochloric acid (HCl) and 0.2 mol L⁻¹ sodium chloride (NaCl). How effective as... show full transcript
Worked Solution & Example Answer:One litre of an aqueous solution is formed from mixing equal volumes of 0.2 mol L⁻¹ hydrochloric acid (HCl) and 0.2 mol L⁻¹ sodium chloride (NaCl) - HSC - SSCE Chemistry - Question 18 - 2017 - Paper 1
Step 1
How effective as a buffer is the aqueous solution formed?
Answer
To determine the effectiveness of the solution as a buffer, it's essential to evaluate the components involved. The solution contains HCl, a strong acid, and NaCl, which provides the conjugate base Cl⁻.
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Understanding Buffers: A buffer solution is defined as one that can resist changes in pH upon the addition of small amounts of acids or bases. For effective buffering, a weak acid must be paired with its conjugate base.
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Analyzing the Components: In this case, HCl is a strong acid and will completely dissociate in solution, meaning it does not maintain the pH effectively. NaCl simply dissociates into its ions (Na⁺ and Cl⁻) and does not contribute to buffering.
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Conjugate Base: While Cl⁻ is the conjugate base of HCl, it derives from a strong acid that does not provide effective resistance to pH changes since it does not re-establish equilibrium under perturbation as weak acids do.
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Final Evaluation: Since HCl dominates due to its strength, any addition of NaOH would shift the pH significantly because the conjugate base (Cl⁻) is ineffective at resisting pH changes. Therefore, the solution cannot be classified as an effective buffer.
Thus, the answer is D: Effective, because the pH would change when a solution of NaOH is added.