Final answer:
The conjugate acid and base of a species are formed by the gain or loss of a proton respectively. For a) H₂O, the conjugate acid is H₃O+ and the conjugate base is OH−.
Step-by-step explanation:
To identify the conjugate acid and conjugate base of each compound, we need to consider what each species would form when it gains or loses a proton (H+).
- H₂O: As a base, it would accept a proton to become H₃O+ (the conjugate acid). As an acid, it would lose a proton to become OH− (the conjugate base).
- HCl (Hydrochloric acid): When HCl donates a proton, it becomes Cl− (the conjugate base). HCl is a strong acid and does not readily accept a proton back, making the concept of its conjugate acid uncommon in practice.
- NH₄+ (Ammonium ion): This species can donate a proton to form NH₃ (ammonia), which is the conjugate base. It does not typically gain protons since it's already positively charged.
- H₂CO₃ (Carbonic acid): When H₂CO₃ loses a proton, it becomes HCO₃− (hydrogen carbonate ion), which is the conjugate base. If it gains a proton, it doesn't form a common species as it already has two protons to donate.