Neco 2022 Chemistry Question 9

Practice objective / multiple choice question 9 from the 2022 Neco Chemistry examination.

Neco 2022 Chemistry Objective / Multiple Choice Medium Difficulty
Question 9 NECO • 2022 • CHEMISTRY • objective

The solubility product of calcium fluoride at 25\,°C is K_{sp}=3.9\times10^{-11}. (a) Calculate the molar solubility \(s\) of CaF_{2} in pure water. (b) If 0.10\,M NaF is added to the solution, determine the new solubility of CaF_{2}. (c) Assuming the fluoride concentration after addition is essentially 0.10\,M, estimate the pH of the solution arising from the hydrolysis of F^{-} (K_{a} of HF = 6.6\times10^{-4}).

Answer Options

A. s = 2.1\\times10^{-4}\\,M; s' (with 0.10\\,M NaF) = 3.9\\times10^{-9}\\,M; pH ≈ 6.8
Correct Answer B. s = 2.1\times10^{-4}\,M; s' (with 0.10\,M NaF) = 3.9\times10^{-9}\,M; pH ≈ 8.1
C. s = 2.1\\times10^{-3}\\,M; s' (with 0.10\\,M NaF) = 3.9\\times10^{-7}\\,M; pH ≈ 9.2
D. s = 1.3\\times10^{-4}\\,M; s' (with 0.10\\,M NaF) = 1.2\\times10^{-8}\\,M; pH ≈ 7.5
Correct Answer
B
Correct Option:
s = 2.1\times10^{-4}\,M; s' (with 0.10\,M NaF) = 3.9\times10^{-9}\,M; pH ≈ 8.1

About This Question

This is Neco 2022 Chemistry Question 9. It is one of the objective questions from the 2022 Neco Chemistry examination.

Difficulty level: Medium .

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