Neco Model Questions Vol1 2025 Chemistry Question 38

Practice objective / multiple choice question 38 from the 2025 Neco Model Questions Vol1 Chemistry examination.

Neco Model Questions Vol1 2025 Chemistry Objective / Multiple Choice Hard Difficulty
Question 38 NECO_MODEL_QUESTIONS_VOL1 • 2025 • CHEMISTRY • objective

A monoprotic weak acid HA (unknown \(K_a\)) is dissolved in 200.0 mL of water, giving a solution that contains 0.0200 mol of HA. The solution is titrated with 0.100 M NaOH. At the half‑equivalence point the pH is measured as 5.20. After adding the exact volume of NaOH required for equivalence, the pH of the resulting solution is 8.95. Determine the acid dissociation constant \(K_a\), the \(pK_a\) of the acid, and the pH at equivalence (the given 8.95 should be confirmed by calculation).

Answer Options

A. K_a = 5.0×10⁻⁶, pK_a = 5.30, pH at equivalence = 8.70
B. K_a = 7.8×10⁻⁶, pK_a = 5.11, pH at equivalence = 9.10
C. K_a = 4.5×10⁻⁶, pK_a = 5.35, pH at equivalence = 8.80
Correct Answer D. K_a = 6.3×10⁻⁶, pK_a = 5.20, pH at equivalence = 8.95
Correct Answer
D
Correct Option:
K_a = 6.3×10⁻⁶, pK_a = 5.20, pH at equivalence = 8.95

About This Question

This is Neco Model Questions Vol1 2025 Chemistry Question 38. It is one of the objective questions from the 2025 Neco Model Questions Vol1 Chemistry examination.

Difficulty level: Hard .

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