Neco 2020 Chemistry Question 47

Practice objective / multiple choice question 47 from the 2020 Neco Chemistry examination.

Neco 2020 Chemistry Objective / Multiple Choice Medium Difficulty

Question 47 NECO • 2020 • CHEMISTRY • objective

A 0.250 M solution of a weak monoprotic acid \(HA\) is titrated at 25 °C with 0.100 M NaOH. After adding 12.5 mL of NaOH the pH is 4.75, and after adding 25.0 mL the pH is 5.30. (i) Determine the acid dissociation constant \(pK_a\) of \(HA\). (ii) Using the obtained \(pK_a\), calculate the pH of a buffer prepared by mixing 40.0 mL of the 0.250 M \(HA\) solution with 20.0 mL of its 0.250 M sodium salt \(NaA\).

A. pK_a = 5.00, buffer pH = 4.90

B. pK_a = 4.95, buffer pH = 4.70

Correct Answer C. pK_a = 5.11, buffer pH = 4.81

D. pK_a = 5.30, buffer pH = 5.00

Correct Answer

Correct Option:

pK_a = 5.11, buffer pH = 4.81

This is Neco 2020 Chemistry Question 47. It is one of the objective questions from the 2020 Neco Chemistry examination.

Difficulty level: Medium .

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