Brønsted–Lowry — the proton-passing game

4 minAS Level7.2.3

AI-drafted, independently checked · not yet teacher-reviewed

By the end of this lesson

By the end you can state the Brønsted–Lowry definitions of acids and bases, identify conjugate acid–base pairs, and explain why water can act as both acid and base.

The 1923 upgrade

Before 1923, acids were "substances that produce H⁺ in water" (Arrhenius). That worked for HCl and NaOH but failed for ammonia and gas-phase reactions.

Johannes Brønsted (Denmark) and Thomas Lowry (England) independently proposed the same idea:

An acid is a proton donor. A base is a proton acceptor.

A proton is just a hydrogen nucleus: $\text{H}^+$ (no electrons, just one proton).

Definition

Brønsted–Lowry acid

A species that donates a proton ( $\text{H}^+$ ) to another species.

Definition

Brønsted–Lowry base

A species that accepts a proton ( $\text{H}^+$ ) from another species.

Acid or base?

Multiple choiceQuestion 1 · Recall

In the Brønsted–Lowry theory, a base is defined as:

AA substance that donates protonsBA substance that accepts protonsCA substance that produces OH⁻ in waterDA substance that accepts electrons

Multiple choiceQuestion 2 · Apply

In the reaction $\text{HCl(aq)} + \text{H}_2\text{O(l)} \rightarrow \text{H}_3\text{O}^+\text{(aq)} + \text{Cl}^-\text{(aq)}$ , which species acts as the Brønsted–Lowry base?

AHClBH₂OCH₃O⁺DCl⁻

Answer the 2 questions above to continue.

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