Conjugate acid-base pairs

1. Acid-Base Reactions

A reaction in which a proton $(H⁺)$ is transferred between substances.

$HCl → H⁺ + Cl⁻$ $H Cl \to H^{+} + C l^{-}$
- $HCl =$ $acid, Cl⁻ =$ conjugate base
$H₂SO₄ → H⁺ + HSO₄⁻$ $H_{2} S O_{4} \to H^{+} + H S O_{4}^{-}$
- $H₂SO₄ = acid, HSO₄⁻$ = conjugate base

$OH⁻ + H⁺ → H₂O$ $O H^{-} + H^{+} \to H_{2} O$
- $OH⁻ =$ $base, H₂O =$ conjugate acid
$HSO₄⁻ + H⁺ → H₂SO₄$ $H S O_{4}^{-} + H^{+} \to H_{2} S O_{4}$
- $HSO₄⁻ = base, H₂SO₄ =$ conjugate acid

Find the acid on the left-hand side of the equation. Label it acid.
Identify its conjugate base on the right-hand side. Label it conjugate base.
Draw a bracket to show the acid-base pair.
Find the base on the left-hand side. Label it base.
Identify its conjugate acid on the right-hand side. Label it conjugate acid.
Draw a bracket to show the base-acid pair.

infoNote

For the reaction:

$HCl + NH₃ → NH₄⁺ + Cl⁻$

Acid	Conjugate Base	Base	Conjugate Acid
$HCl$	$Cl⁻$	$NH₃$	$NH₄⁺$

Type	Reaction	Example
Conjugate Acid	$Base + H⁺ → Conjugate Acid$	$OH⁻ + H⁺ → H₂O$
Conjugate Base	$Acid • H⁺ → Conjugate Base$	$HCl → H⁺ + Cl⁻$