Gce Model Questions Vol1 2017 Chemistry Question 6

Practice objective / multiple choice question 6 from the 2017 Gce Model Questions Vol1 Chemistry examination.

Gce Model Questions Vol1 2017 Chemistry Objective / Multiple Choice Medium Difficulty
Question 6 GCE_MODEL_QUESTIONS_VOL1 • 2017 • CHEMISTRY • objective

A \(25.0\ \text{mL}\) sample of a weak monoprotic acid HA is titrated with \(0.100\ \text{M}\) NaOH. At the half‑equivalence point the measured pH is \(4.75\). After adding \(12.5\ \text{mL}\) of NaOH the pH is \(9.20\). Determine (a) the acid dissociation constant \(K_a\) of HA and (b) the initial concentration of HA in the sample.

Answer Options

A. K_a = 1.78×10⁻⁵; initial concentration = 0.0600 M
B. K_a = 2.10×10⁻⁵; initial concentration = 0.0450 M
Correct Answer C. K_a = 1.78×10⁻⁵; initial concentration = 0.0500 M
D. K_a = 1.78×10⁻⁴; initial concentration = 0.0500 M
Correct Answer
C
Correct Option:
K_a = 1.78×10⁻⁵; initial concentration = 0.0500 M

About This Question

This is Gce Model Questions Vol1 2017 Chemistry Question 6. It is one of the objective questions from the 2017 Gce Model Questions Vol1 Chemistry examination.

Difficulty level: Medium .

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