CAIE A-Level Chemistry 25.1.2 Conjugate Acid–Base Pairs

Practise defining a conjugate pair and identifying both acid/base pairs in proton-transfer reactions.

Exam points

define a conjugate acid–base pair as two species that differ by exactly one H+
pair each proton donor with the species left after donation and each acceptor with its protonated form
for HPO4²− or other amphiprotic ions, derive both conjugate acid and conjugate base with charges

[Maximum number: 2]

(a)

Define conjugate acid-base pair.

[ 1 ]

two species that differ by one proton / $\mathrm{H}^{+}$

(b)

Give the formulas of the conjugate acid and the conjugate base of the hydrogen phosphate ion, $\mathrm{HPO}_{4}{ }^{2-}$ .

\begin{aligned} & \text { conjugate acid of } \mathrm{HPO}_{4}^{2-} \\ & \text { conjugate base of } \mathrm{HPO}_{4}^{2-} \end{aligned}

[ 1 ]

$\mathrm{H}_{2} \mathrm{PO}_{4}{ }^{-}$ AND PO4 ${ }^{3-}$

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