Neco Model Questions Vol1 2021 Chemistry Question 26

Practice objective / multiple choice question 26 from the 2021 Neco Model Questions Vol1 Chemistry examination.

Neco Model Questions Vol1 2021 Chemistry Objective / Multiple Choice Medium Difficulty
Question 26 NECO_MODEL_QUESTIONS_VOL1 • 2021 • CHEMISTRY • objective

A saturated solution of calcium fluoride, CaF\(_2\) (\(K_{sp}=1.5\times10^{-10}\)), is prepared. (a) Calculate the molar solubility of CaF\(_2\) in pure water. (b) If the solution already contains 0.10 M NaF, what is the new molar solubility? (c) The solution is then acidified to pH 4.0; assuming the equilibrium \(\mathrm{HF \rightleftharpoons H^{+}+F^{-}}\) with \(K_a=6.6\times10^{-4}\), calculate the molar solubility under these acidic conditions.

Answer Options

A. (a) 3.0×10⁻⁴ M; (b) 1.0×10⁻⁷ M; (c) 2.5×10⁻⁸ M
Correct Answer B. (a) 3.3×10⁻⁴ M; (b) 1.5×10⁻⁸ M; (c) 2.0×10⁻⁸ M
C. (a) 4.0×10⁻⁴ M; (b) 5.0×10⁻⁹ M; (c) 1.5×10⁻⁸ M
D. (a) 2.5×10⁻⁴ M; (b) 2.0×10⁻⁸ M; (c) 3.5×10⁻⁸ M
Correct Answer
B
Correct Option:
(a) 3.3×10⁻⁴ M; (b) 1.5×10⁻⁸ M; (c) 2.0×10⁻⁸ M

About This Question

This is Neco Model Questions Vol1 2021 Chemistry Question 26. It is one of the objective questions from the 2021 Neco Model Questions Vol1 Chemistry examination.

Difficulty level: Medium .

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