Acid–base reactions — proton transfers in action

5 minAS Level7.2.4

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

By the end of this lesson

By the end you can write balanced equations for Brønsted–Lowry acid–base reactions, identify both conjugate pairs, and predict the direction of proton transfer using relative acid/base strength.

The proton transfer equation

Every Brønsted–Lowry reaction is a proton transfer from an acid to a base:

$\text{Acid}_1 + \text{Base}_2 \rightleftharpoons \text{Conjugate base}_1 + \text{Conjugate acid}_2$

Two conjugate pairs, four species total. The proton moves from Acid₁ to Base₂.

Worked example: HCl + NH₃

Write the Brønsted–Lowry equation for HCl reacting with NH₃ and label all four species.

Have a go first?

Write the equation

Fill in the blanksQuestion 1 · Apply

Complete the Brønsted–Lowry equation for nitric acid reacting with ammonia: HNO₃ + NH₃ ⇌ +

Multiple choiceQuestion 2 · Apply

In the reaction $\text{H}_2\text{SO}_4 + \text{H}_2\text{O} \rightleftharpoons \text{HSO}_4^- + \text{H}_3\text{O}^+$ , which is the conjugate acid–base pair for water?

AH₂O / HSO₄⁻BH₂O / H₃O⁺CH₂SO₄ / H₃O⁺DHSO₄⁻ / H₃O⁺

Answer the 2 questions above to continue.

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