Final answer:
The conjugate acid of H₂O is H₃O⁺ (hydronium ion), and the conjugate base of O²⁻ is O₂²⁻ (peroxide ion).
Step-by-step explanation:
In acid-base chemistry, a conjugate acid forms when a base gains a proton, and a conjugate base forms when an acid loses a proton. H₂O can act as both an acid and a base. When it accepts a proton, it forms the hydronium ion (H₃O⁺), making H₃O⁺ the conjugate acid of H₂O. On the other hand, when H₂O loses a proton, it forms the hydroxide ion (OH⁻), the conjugate base of H₂O.
For O²⁻, it can act as a base, accepting a proton to form OOH⁻ (superoxide ion), making OOH⁻ the conjugate acid of O²⁻. When O²⁻ loses a proton, it forms O₂²⁻, the conjugate base of O²⁻.
Understanding conjugate acids and bases is crucial in acid-base reactions, providing insights into how substances donate or accept protons in various chemical processes.