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Introduction to Acid-Base Reactions

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In the Brønsted-Lowry model, an acid-base reaction is a proton (H⁺) transfer: the acid donates a proton and the base accepts one. When ammonia reacts with water, ammonia (the base) takes a proton, forming NH₄⁺, and water acts as the acid. Every acid-base reaction has a donor and an acceptor.

UNIT 4 TOPIC 4.8 • INTRODUCTION TO ACID-BASE REACTIONS PROTON TRANSFER BRØNSTED–LOWRY IDEA Acid donates H⁺. Base accepts H⁺. Follow the proton. WORKED EXAMPLE + ⇌ + NH₃ base H₂O acid NH₄⁺ conj. acid OH⁻ conj. base H⁺ transfer NH₃ / NH₄⁺ differ by one H⁺ H₂O / OH⁻ differ by one H⁺ WATER CAN DO BOTH H₂O as acid donates H⁺ → OH⁻ H₂O as base accepts H⁺ → H₃O⁺ Water is amphoteric — it can act as an acid or a base, so it often takes part directly in aqueous acid– base reactions. CONJUGATE PAIR CHECK A conjugate acid–base pair differs by exactly one proton, H⁺. Charge changes by +1 when a species gains H⁺, and by −1 when it loses H⁺. AP Chemistry · Unit 4 · Chemical Reactions
The Brønsted-Lowry idea: acid-base reactions are proton (H⁺) transfers. An acid donates a proton and a base accepts one — for example, ammonia (a base) takes a proton from water. Identifying donor and acceptor is the core move.
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The core skill is tracking the proton: which species gives an H⁺ (acid) and which takes it (base). Once you follow the proton, the conjugate acid-base pairs and the direction of transfer fall into place.

The work

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Lesson
Acid-Base Reactions ›

Brønsted-Lowry acid-base reactions are proton transfers between a donor and an acceptor. The lesson tracks the proton and identifies acid and base, then closes with a ten-scenario check.

Skill check · 10 scenarios
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Diagnostic
10-item topic check ›

Ten items on Brønsted-Lowry acid-base reactions: identifying the proton donor (acid) and acceptor (base) and following the H⁺ transfer.

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Targeted Practice
Drill a single misconception ›

Pick one of the failure modes you missed and drill it on its own. The round is adaptive: two correct in a row clears the misconception and moves you to the next.

Take the diagnostic to identify your misconceptions
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