IB Chemistry HL 3.1.2 Conjugate Acid Base Pairs Questions

Use real HL exam questions to identify conjugate pairs, draw conjugate structures and compare proton-transfer roles.

Exam points

Identify conjugate acid–base pairs as species differing by one proton.
Deduce the formula or structure of a conjugate base, including ionic forms of carboxylic acids.
Use proton transfer and charge to distinguish the conjugate base of an acid from an unrelated structural change and compare acid strength where assessed.

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Study 3.1.2—Conjugate acid-base pairs conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

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Nitrous acid, $\mathrm{HNO}_{2}$ , is a weak acid which can be used to make acidic buffers.

A $1.00 \mathrm{~mol} \mathrm{dm}^{-3}$ solution of nitrous acid was prepared. This solution contains two conjugate acid-base pairs.

State the formulas of the conjugate acid and conjugate base in each pair.

Conjugate acid:
Conjugate base:
Conjugate acid:
Conjugate base:

（a）

（i）

conjugate acid $\mathrm{H}_{3} \mathrm{O}^{+}$ «（aq）» AND conjugate base $\mathrm{H}_{2} \mathrm{O}$ « $(\mathrm{l}) »$
conjugate acid $\mathrm{HNO}_{2}$ «（aq）» AND conjugate base $\mathrm{NO}_{2}{ }^{-}$ «（aq）»

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IB Chemistry HL 3.1.2 Conjugate Acid Base Pairs Questions question 1