In Bronsted-Lowry terms, which statement correctly describes ammonia (NH3) acting as a base?

In Bronsted-Lowry terms, which statement correctly describes ammonia (NH3) acting as a base?

• A. Accepts a proton.
• B. Donates a proton.
• C. Donates an electron pair.
• D. Acts as an acid.

Answer: (A)

In Bronsted-Lowry terms, a base is a substance that accepts a proton. Ammonia has a lone pair on nitrogen that can accept a hydrogen ion, so it behaves as a base by forming the ammonium ion NH4+ when it captures H+. For example, NH3 + H+ → NH4+, and in water this shows up as NH3 + H2O ⇌ NH4+ + OH−, demonstrating base behavior by taking a proton and producing a conjugate acid. Donating a proton would describe acid behavior, not what ammonia does here, and donating an electron pair is a Lewis-base concept, not Bronsted-Lowry. Acting as an acid would be incorrect for this basic reaction.

In Bronsted-Lowry terms, a base is a substance that accepts a proton. Ammonia has a lone pair on nitrogen that can accept a hydrogen ion, so it behaves as a base by forming the ammonium ion NH4+ when it captures H+. For example, NH3 + H+ → NH4+, and in water this shows up as NH3 + H2O ⇌ NH4+ + OH−, demonstrating base behavior by taking a proton and producing a conjugate acid. Donating a proton would describe acid behavior, not what ammonia does here, and donating an electron pair is a Lewis-base concept, not Bronsted-Lowry. Acting as an acid would be incorrect for this basic reaction.