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PCAT Chemical Processes – Increasing pKa

  • by Sam
  • Dec 18, 2017
  • PCAT Question of the Day

Which of the following correctly lists the reagents in terms of increasing pKa?

A) Nitric Acid, Acetic Acid, Calcium Hydroxide

B) Calcium Hydroxide, Acetic Acid, Nitric Acid

C) Acetic Acid, Nitric Acid, Calcium Hydroxide

D) Calcium Hydroxide, Nitric Acid, Acetic Acid

Click for Explanation

The reagents listed are all common ones that the MCAT will expect you to be familiar with:

Nitric Acid: HNO3, strong acid, pKa = -1.4

Acetic Acid: CH3COOH, weak acid, pKa = 4.76

Calcium Hydroxide: Ca(OH)2, strong base, pKa = 12.4

Acid strength correlates with pKa, so choice (A) is correct.

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