Neco 2018 Chemistry Question 47

Practice objective / multiple choice question 47 from the 2018 Neco Chemistry examination.

Neco 2018 Chemistry Objective / Multiple Choice Hard Difficulty
Question 47 NECO • 2018 • CHEMISTRY • objective

A 0.250 M aqueous solution of a monoprotic weak acid \(HA\) has an unknown acid dissociation constant \(K_{a}\). When 0.050 mol of its sodium salt \(NaA\) is added to 1.00 L of this solution, the pH becomes 5.00. Determine the original concentration of \(HA\) before the salt was added and calculate \(K_{a}\) of the acid.

Answer Options

Correct Answer A. Initial \([HA]\) = 5.9×10⁻² M; \(K_{a}=1.8\times10^{-6}\)
B. Initial \\([HA]\\) = 4.2×10⁻² M; \\(K_{a}=2.5\\times10^{-6}\\)
C. Initial \\([HA]\\) = 6.8×10⁻² M; \\(K_{a}=1.2\\times10^{-6}\\)
D. Initial \\([HA]\\) = 5.0×10⁻² M; \\(K_{a}=3.0\\times10^{-6}\\)
Correct Answer
A
Correct Option:
Initial \([HA]\) = 5.9×10⁻² M; \(K_{a}=1.8\times10^{-6}\)

About This Question

This is Neco 2018 Chemistry Question 47. It is one of the objective questions from the 2018 Neco Chemistry examination.

Difficulty level: Hard .

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