In the Brønsted–Lowry definition, what is the conjugate base of the ammonium ion $N_4^{+}$ (often written as $N_{4}H+$)?

• A. $N_{3}H$
• B. $N_{2}H$
• C. $N_{4}H$
• D. $N_4^{+}$

Answer: (A)

Verified step by step guidance

1. Recall the Brønsted–Lowry definition of acids and bases: an acid is a proton (H⁺) donor, and a base is a proton acceptor.
2. Identify the ammonium ion, \( \mathrm{NH_4^+} \), as the species that can donate a proton (H⁺) because it carries a positive charge and has an extra hydrogen compared to ammonia.
3. Determine the conjugate base by removing one proton (H⁺) from the ammonium ion. This means subtracting one hydrogen ion from \( \mathrm{NH_4^+} \).
4. Write the formula of the species left after the proton is removed. Removing one H⁺ from \( \mathrm{NH_4^+} \) results in \( \mathrm{NH_3} \), which is ammonia.
5. Conclude that the conjugate base of the ammonium ion \( \mathrm{NH_4^+} \) is ammonia, \( \mathrm{NH_3} \).