A chemist needs to make a buffer solution with a pH of 4.90, and she has access to the following
acid/conjugate base pairs in her lab. Based on the Ka values given for the acids, which pair would be
the best choice to use to make this buffer?
A. Chlorous acid / chlorite (Ka = 1.10×10-2)
B. Phosphoric acid / phosphate (Ka = 7.52×10-3)
C. Acetic acid / acetate (Ka = 1.76×10-5)
D. Carbonic acid / bicarbonate (Ka = 4.30×10-7)
E. Hypochlorous acid / hypochlorite (Ka = 3.50×10-8)

Question

A chemist needs to make a buffer solution with a pH of 4.90, and she has access to the following
acid/conjugate base pairs in her lab. Based on the Ka values given for the acids, which pair would be
the best choice to use to make this buffer?
A. Chlorous acid / chlorite (Ka = 1.10×10-2)
B. Phosphoric acid / phosphate (Ka = 7.52×10-3)
C. Acetic acid / acetate (Ka = 1.76×10-5)
D. Carbonic acid / bicarbonate (Ka = 4.30×10-7)
E. Hypochlorous acid / hypochlorite (Ka = 3.50×10-8)

Accepted Answer

***D*** ∻Key Concept∻ ⚹Buffer solutions and pKa values⚹ ∻Explanation∻ ⚹To create a buffer at pH 4.90, we need an acid with a pKa close to this value. The best choice is Carbonic acid / Bicarbonate, as its pKa is closest to 4.90.⚹◊Which equation can be used to calculate the pH of a buffer solution, and how does the ratio of the acid to its conjugate base affect the pH?⍭ Generate me a similar question◊

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