Question

Indicate whether each of the following statements is correct or incorrect. For those that are incorrect, explain why they are wrong. (a) Every Bronsted-Lowry acid is also a Lewis acid. (b) Every Lewis acid is also a Bronsted-Lowry acid. (c) Conjugate acids of weak bases produce more acidic solutions than conjugate acids of strong bases. (d) \(\mathrm{K}^{+}\) ion is acidic in water because it causes hydrating water molecules to become more acidic. (e) The percent ionization of a weak acid in water increases as the concentration of acid decreases.

Short answer

(a) Correct - Every Bronsted-Lowry acid is also a Lewis acid since donating a proton involves accepting an electron pair. (b) Incorrect - Not every Lewis acid is a Bronsted-Lowry acid, as some Lewis acids, like metal cations, do not donate protons. (c) Correct - Conjugate acids of weak bases produce more acidic solutions, as they have a higher tendency to donate protons. (d) Incorrect - \(\mathrm{K}^{+}\) ion is considered neutral in water because it does not affect the acidity or basicity of water. (e) Correct - The percent ionization of a weak acid increases as the concentration of acid decreases, due to fewer acid molecules interacting with each other.

Step-by-step solution

Statement (a)

Every Bronsted-Lowry acid is also a Lewis acid. This statement is correct. A Bronsted-Lowry acid is a substance that donates a proton (H+) to another substance. A Lewis acid is a substance that accepts an electron pair. Since donating a proton also involves accepting an electron pair, every Bronsted-Lowry acid can be classified as a Lewis acid.

Statement (b)

Every Lewis acid is also a Bronsted-Lowry acid. This statement is incorrect. A Lewis acid is a substance that can accept an electron pair, but it does not need to donate a proton in doing so. Hence, not every Lewis acid can be classified as a Bronsted-Lowry acid. For example, metal cations like Al^3+ are Lewis acids but not Bronsted-Lowry acids, as they do not donate protons.

Statement (c)

Conjugate acids of weak bases produce more acidic solutions than conjugate acids of strong bases. This statement is correct. Conjugate acids are formed from bases by accepting a proton. The conjugate acid of a weak base has a higher tendency to donate protons, resulting in a more acidic solution as compared to the conjugate acid of a strong base, which has a lower tendency to donate protons.

Statement (d)

\(\mathrm{K}^{+}\) ion is acidic in water because it causes hydrating water molecules to become more acidic. This statement is incorrect. Although \(\mathrm{K}^{+}\) ion can strongly hydrate water molecules, it does not cause them to become more acidic. Instead, \(\mathrm{K}^{+}\) ion and similar alkali metal ions are considered to be neutral in water since they do not affect the acidity or basicity of water.

Statement (e)

The percent ionization of a weak acid in water increases as the concentration of acid decreases. This statement is correct. The percent ionization of a weak acid is given by the ratio of the ionized acid concentration to the initial acid concentration. When the concentration of a weak acid in water decreases, there are fewer acid molecules to interact with each other, resulting in a higher probability of the acid molecules ionizing. Thus, the percent ionization increases as the concentration of the weak acid decreases.