Final answer:
NH₃ acts as a conjugate base in the reaction NH₃ + H₂O → NH₄⁺ + OH⁻, and as a conjugate acid in NH₂⁻ + H⁺ → NH₃. The ability to gain or lose a proton makes NH₃ an amphiprotic species.
Step-by-step explanation:
The question asks which equations represent ammonia (NH₃) as a conjugate acid and a conjugate base. The correct equations are:
- As a conjugate base: NH₃ + H₂O → NH₄⁺ + OH⁻
- As a conjugate acid: NH₂⁻ + H⁺ → NH₃
Equation (a) NH₄⁺ → NH₃ + H⁺ shows ammonia acting as a conjugate base, and equation (d) NH₃ + H⁺ → NH₄⁺ shows it as a conjugate acid. The transfer of a proton defines the acid-base reaction, making ammonia an amphiprotic species as it can both gain and lose a proton.