In each pair, select the stronger acid. (a) Pyruvic acid (p Ka=2.49) or lactic acid (p Ka=3.08)

step 1 When determining the strength of acids, there's a couple options you have from this chapter. You

In each pair, select the stronger acid. (a) Pyruvic acid (p...

In each pair, select the stronger acid. (a) Pyruvic acid $\left(\mathrm{p} K_{\mathrm{a}}=2.49\right)$ or lactic acid $\left(p K_{a}=3.08\right)$ (b) Citric acid $\left(\mathrm{p} K_{\mathrm{a}}=3.08\right)$ or phosphoric acid $\left(p K_{\mathrm{a}}=2.10\right)$ (c) Benzoic acid $\left(K_{\mathrm{a}}=6.5 \times 10^{-5}\right)$ or lactic acid $\left(K_{\mathrm{a}}=8.4 \times 10^{-4}\right)$ (d) Carbonic acid $\left(K_{\mathrm{a}}=4.3 \times 10^{-7}\right)$ or boric acid $\left(K_{\mathrm{a}}=7.3 \times 10^{-10}\right)$

In each pair, select the stronger acid.
(a) Pyruvic acid $\left(\mathrm{p} K_{\mathrm{a}}=2.49\right)$ or lactic acid $\left(p K_{a}=3.08\right)$
(b) Citric acid $\left(\mathrm{p} K_{\mathrm{a}}=3.08\right)$ or phosphoric acid $\left(p K_{\mathrm{a}}=2.10\right)$
(c) Benzoic acid $\left(K_{\mathrm{a}}=6.5 \times 10^{-5}\right)$ or lactic acid $\left(K_{\mathrm{a}}=8.4 \times 10^{-4}\right)$
(d) Carbonic acid $\left(K_{\mathrm{a}}=4.3 \times 10^{-7}\right)$ or boric acid $\left(K_{\mathrm{a}}=7.3 \times 10^{-10}\right)$

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Key Concepts

Acid Dissociation Constant (Ka)

The acid dissociation constant, Ka, quantifies the extent to which an acid donates protons in a solution. It is a numerical value derived from the equilibrium concentrations of the acid, its conjugate base, and hydrogen ions. A larger Ka indicates a stronger acid because it implies a greater degree of ionization in solution.

pKa as a Measure of Acid Strength

The pKa is defined as the negative logarithm of the acid dissociation constant (pKa = -log Ka). It serves as a convenient scale for comparing acid strengths; lower pKa values correspond to stronger acids because they reflect a higher Ka. This logarithmic scale makes small differences in proton-donating ability easier to compare.

Comparative Acid Strength

When comparing acids, one examines either the Ka values or the pKa values. A higher Ka or a lower pKa signifies a stronger acid. This principle allows chemists to predict reaction outcomes and understand the behavior of acids in various chemical contexts, making it a fundamental concept in acid-base chemistry.

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