Strong and Weak Acids and Bases in Aqueous Solution Identify each of the following as a strong acid, weak acid, strong base, or weak base. Write an equation to describe its reaction with water.(a) CH3CH2NH2(aq)(b) HF(aq)(c) NaF(aq)(d) KOH(aq)

Question

Strong and Weak Acids and Bases in Aqueous Solution

Identify each of the following as a strong acid, weak acid, strong base, or weak base. Write an equation to describe its reaction with water.

(a) CH₃CH₂NH₂(aq)

(b) HF(aq)

(c) NaF(aq)

(d) KOH(aq)

Accepted Answer

(a) The compound CH₃CH₂NH₂ is an organic compound called an amine because it contains the —NH₂ group. It is a weak base like NH₃. The equation for its ionization in water is

[latex]CH_{3}CH_{2}NH_{2}(aq)+H_{2}O(l) \xrightleftharpoons[]{} CH_{3}CH_{2}NH^{+}_{3}(aq)+OH^{-}(aq)[/latex]

Because CH₃CH₂NH₂ is a base, it ionizes in water to form OH^-(aq) ions. Equilibrium arrows are used because CH₃CH₂NH₂ is a weak base and ionizes only partially.

(b) Hydrofluoric acid, HF, is an acid. Since it is not on the list of strong acids in Table 13.1, it is a weak acid. The equation for its ionization in water is

[latex]HF(aq)+H_{2}O(l) \xrightleftharpoons[]{} F^{-}(aq) +H_{3}O^{+}(aq)[/latex]

Because HF is an acid, it reacts with water to form H₃O⁺(aq) ions. Equilibrium arrows are used because HF is a weak acid and ionizes only partially.

TABLE 13.1 | Common Strong Acids

Name	Formula
hydrochloric acid	HCl
hydrobromic acid	HBr
hydroiodic acid	HI
nitric acid	HNO₃
chloric acid	HClO₃
perchloric acid	HClO₄
sulfuric acid (only one H⁺ ionizes completely)	H₂SO₄

(c) Sodium fluoride is an ionic compound that completely dissociates in water to form Na⁺(aq) and F^–(aq). The F^– ion is the conjugate base of the weak acid HF, so it is a weak base. The equation for its reaction with water is

[latex]F^{-}(aq)+H_{2}O(l) \xrightleftharpoons[]{} HF(aq) +OH^{-}(aq)[/latex]

Because F^– is a base, it reacts with water to form OH^– ions. Equilibrium arrows are used because F ^– is a weak base.

(d) KOH is a strong base because it is a group IA (1) metal hydroxide. The equation for its dissociation in water is

KOH(aq) → K⁺(aq) + OH^–(aq)

Because KOH is a base, it produces hydroxide ions in water. A one-directional arrow is used because KOH is a strong base and dissociates completely.

Question 13.4: Strong and Weak Acids and Bases in Aqueous Solution Identify...

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