Neco 2023 Chemistry Question 7

Practice essay / theory question 7 from the 2023 Neco Chemistry examination. This question covers Acids, Bases, Salts, Buffer solutions, Acid‑base titration .

Neco 2023 Chemistry Essay / Theory
Topics: Acids Bases Salts Buffer solutions Acid‑base titration
Question 7 NECO • 2023 • CHEMISTRY • essay

A 0.250 mol sample of sodium carbonate (Na₂CO₃) is dissolved in 500.0 mL of water to give a clear solution. The solution is titrated with 0.1000 M hydrochloric acid (HCl). The carbonate ion (CO₃²⁻) behaves as a diprotic base in water. The acid‑dissociation constants for carbonic acid are Ka₁ = 4.3×10⁻⁷ and Ka₂ = 5.6×10⁻¹¹.

Question Parts

( a )
Write the balanced chemical equations for the stepwise neutralisation of the carbonate ion by HCl.
( b )
Calculate the pH of the solution after the addition of 12.5 mL of the 0.1000 M HCl solution. (Hint: at this stage the system consists of the conjugate base CO₃²⁻ and its conjugate acid HCO₃⁻, forming a buffer.)
( c )
Determine the volume of 0.1000 M HCl required to reach the equivalence point for the second neutralisation (complete conversion of HCO₃⁻ to H₂CO₃) and state the pH of the solution at that point.
( d )
Discuss qualitatively how the titration curve would change if the initial sodium carbonate solution were diluted to 1.00 L before titration, keeping the amount of Na₂CO₃ the same.

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About This Question

This is Neco 2023 Chemistry Question 7. It is one of the essay questions from the 2023 Neco Chemistry examination.

The question covers Acids, Bases, Salts, Buffer solutions, Acid‑base titration .

View More Neco 2023 Chemistry Questions More Neco Practice Questions Back to Questions

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