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IB Chemistry HL 3.2.1 Oxidation and reduction Question Bank

Practise IB Chemistry HL 3.2.1 by applying oxidation and reduction to exam-style questions.

Syllabus
First assessment 2025
Course
Chemistry HL
Level
HL

Exam points

  • identify the relevant chemical structure, process or evidence
  • apply the correct chemical model or equation
  • evaluate the result using chemical reasoning and data

3.2.1—Oxidation and reduction question 1

[Maximum number: 3]

Phosphine (IUPAC name phosphane) is a hydride of phosphorus, with the formula PH3\mathrm{PH}_{3}.

Phosphine is usually prepared by heating white phosphorus, one of the allotropes of phosphorus, with concentrated aqueous sodium hydroxide. The equation for the reaction is:

P4( s)+3OH−(aq)+3H2O(l)→PH3( g)+3H2PO2−(aq)\mathrm{P}_{4}(\mathrm{~s})+3 \mathrm{OH}^{-}(\mathrm{aq})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{PH}_{3}(\mathrm{~g})+3 \mathrm{H}_{2} \mathrm{PO}_{2}^{-}(\mathrm{aq})

Oxidation is now defined in terms of change of oxidation number. Explore how earlier definitions of oxidation and reduction may have led to conflicting answers for the conversion of P4\mathrm{P}_{4} to H2PO2−\mathrm{H}_{2} \mathrm{PO}_{2}^{-}and the way in which the use of oxidation numbers has resolved this.

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