Gce Model Questions Vol1 2020 Chemistry Question 42

Practice objective / multiple choice question 42 from the 2020 Gce Model Questions Vol1 Chemistry examination.

Gce Model Questions Vol1 2020 Chemistry Objective / Multiple Choice Hard Difficulty

Question 42 GCE_MODEL_QUESTIONS_VOL1 • 2020 • CHEMISTRY • objective

Solution A contains a weak acid HA (\(K_a = 1.8\times10^{-5}\)) at a concentration of 0.020 M and its conjugate base A⁻ at 0.030 M. (a) Calculate the pH of the solution using the Henderson-Hasselbalch equation. (b) How many millimoles of a strong acid (e.g., HCl) must be added to 250 mL of this buffer to lower the pH by exactly 0.10 units? Assume the volume change is negligible.

Answer Options

A. pH = 4.92; 0.55 mmol HCl

Correct Answer B. pH = 4.92; 0.71 mmol HCl

C. pH = 4.80; 0.60 mmol HCl

D. pH = 5.02; 0.85 mmol HCl

Correct Answer

Correct Option:

pH = 4.92; 0.71 mmol HCl

About This Question

This is Gce Model Questions Vol1 2020 Chemistry Question 42. It is one of the objective questions from the 2020 Gce Model Questions Vol1 Chemistry examination.

Difficulty level: Hard .

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