Neco 2025 Chemistry Question 7

Practice essay / theory question 7 from the 2025 Neco Chemistry examination. This question covers Acids, Bases and Salts, Buffer solutions, Henderson‑Hasselbalch equation, Titration of weak base with strong acid, Common‑ion effect .

Neco 2025 Chemistry Essay / Theory
Topics: Acids, Bases and Salts Buffer solutions Henderson‑Hasselbalch equation Titration of weak base with strong acid Common‑ion effect
Question 7 NECO • 2025 • CHEMISTRY • essay

A student is required to prepare a buffer solution using acetic acid (CH\(_3\)COOH) and sodium acetate (CH\(_3\)COONa) and to determine its pH. The student also titrates a weak base with a strong acid and later adds a soluble salt to the titrated mixture. Answer the following.

Question Parts

( a )
Calculate the pH of a buffer that contains 0.250 mol of acetic acid and 0.150 mol of sodium acetate dissolved in 1.00 L of water. Given \(K_a\) of acetic acid = 1.8 \times 10^{-5}.
( b )
The student titrates 25.0 mL of 0.100 M ammonia (NH\(_3\)) with 0.100 M hydrochloric acid (HCl). Determine the pH of the solution at the half‑equivalence point, showing all reasoning.
( c )
After the titration is complete, the student adds 0.020 mol of NaCl to the solution. Explain qualitatively how the pH will be affected and why, referring to the common‑ion effect.

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About This Question

This is Neco 2025 Chemistry Question 7. It is one of the essay questions from the 2025 Neco Chemistry examination.

The question covers Acids, Bases and Salts, Buffer solutions, Henderson‑Hasselbalch equation, Titration of weak base with strong acid, Common‑ion effect .

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