Neco 2018 Chemistry Question 38

Practice objective / multiple choice question 38 from the 2018 Neco Chemistry examination.

Neco 2018 Chemistry Objective / Multiple Choice Medium Difficulty
Question 38 NECO • 2018 • CHEMISTRY • objective

A buffer solution is prepared by mixing a weak acid HA ( \(K_a = 1.8 \times 10^{-5}\) ) with its sodium salt NaA. The pH of the buffer is adjusted to 5.00. (a) Calculate the required ratio \([\ce{A^-}]/[\ce{HA}]\). (b) If the solution is to contain 0.20 mol of \(\ce{A^-}\) in a total volume of 250.0 mL, determine the mass of HA (molar mass \(60\ \text{g mol}^{-1}\)) that must be added.

Answer Options

Correct Answer A. Required ratio \([\ce{A^-}]/[\ce{HA}] = 1.80\); mass of HA = 6.67 g.
B. Required ratio \([\ce{A^-}]\/[\ce{HA}] = 2.50\); mass of HA = 5.00 g.
C. Required ratio \([\ce{A^-}]\/[\ce{HA}] = 0.56\); mass of HA = 9.45 g.
D. Required ratio \([\ce{A^-}]\/[\ce{HA}] = 1.20\); mass of HA = 7.80 g.
Correct Answer
A
Correct Option:
Required ratio \([\ce{A^-}]/[\ce{HA}] = 1.80\); mass of HA = 6.67 g.

About This Question

This is Neco 2018 Chemistry Question 38. It is one of the objective questions from the 2018 Neco Chemistry examination.

Difficulty level: Medium .

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