Question

For each of the following aqueous reactions, identify the acid, the base, the conjugate base, and the conjugate acid. a. \(\mathrm{H}_{2} \mathrm{O}+\mathrm{H}_{2} \mathrm{CO}_{3} \rightleftharpoons \mathrm{H}_{3} \mathrm{O}^{+}+\mathrm{HCO}_{3}^{-}\) b. \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}+\mathrm{H}_{3} \mathrm{O}^{+}\) c. \(\mathrm{HCO}_{3}^{-}+\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+} \rightleftharpoons \mathrm{H}_{2} \mathrm{CO}_{3}+\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}\)

Short answer

a. Acid: \(\mathrm{H}_{2} \mathrm{CO}_{3}\), Base: \(\mathrm{H}_{2} \mathrm{O}\), Conjugate acid: \(\mathrm{H}_{3} \mathrm{O}^{+}\), Conjugate base: \(\mathrm{HCO}_{3}^{-}\) b. Acid: \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+}\), Base: \(\mathrm{H}_{2} \mathrm{O}\), Conjugate acid: \(\mathrm{H}_{3} \mathrm{O}^{+}\), Conjugate base: \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}\) c. Acid: \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+}\), Base: \(\mathrm{HCO}_{3}^{-}\), Conjugate acid: \(\mathrm{H}_{2} \mathrm{CO}_{3}\), Conjugate base: \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}\)

Step-by-step solution

Identify the acid

In this reaction, \(\mathrm{H}_{2} \mathrm{CO}_{3}\) donates a hydrogen ion to the water, so it is the acid.

Identify the base

In this reaction, \(\mathrm{H}_{2} \mathrm{O}\) accepts the hydrogen ion from the acid, so it is the base.

Identify the conjugate acid

After accepting a hydrogen ion from the acid, the \(\mathrm{H}_{2} \mathrm{O}\) becomes \(\mathrm{H}_{3} \mathrm{O}^{+}\), so this is the conjugate acid.

Identify the conjugate base

After donating its hydrogen ion, the \(\mathrm{H}_{2} \mathrm{CO}_{3}\) becomes \(\mathrm{HCO}_{3}^{-}\), so this is the conjugate base. b. Identify the acid, base, conjugate acid, and conjugate base \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}+\mathrm{H}_{3} \mathrm{O}^{+}\)

Identify the acid

In this reaction, \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+}\) donates a hydrogen ion to the water, so it is the acid.

Identify the base

In this reaction, \(\mathrm{H}_{2} \mathrm{O}\) accepts the hydrogen ion from the acid, so it is the base.

Identify the conjugate acid

After accepting a hydrogen ion from the acid, the \(\mathrm{H}_{2} \mathrm{O}\) becomes \(\mathrm{H}_{3} \mathrm{O}^{+}\), so this is the conjugate acid.

Identify the conjugate base

After donating its hydrogen ion, the \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+}\) becomes \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}\), so this is the conjugate base. c. Identify the acid, base, conjugate acid, and conjugate base \(\mathrm{HCO}_{3}^{-}+\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+} \rightleftharpoons \mathrm{H}_{2} \mathrm{CO}_{3}+\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}\)

Identify the acid

In this reaction, \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+}\) donates a hydrogen ion to \(\mathrm{HCO}_{3}^{-}\), so it is the acid.

Identify the base

In this reaction, \(\mathrm{HCO}_{3}^{-}\) accepts the hydrogen ion from the acid, so it is the base.

Identify the conjugate acid

After accepting a hydrogen ion from the acid, the \(\mathrm{HCO}_{3}^{-}\) becomes \(\mathrm{H}_{2} \mathrm{CO}_{3}\), so this is the conjugate acid.

Identify the conjugate base

After donating its hydrogen ion, the \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+}\) becomes \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}\), so this is the conjugate base.