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CAIE IGCSE Chemistry 6.4.10 Redox Reactions By the Colour Changes Questions

Use acidified potassium manganate(VII) and potassium iodide colour changes to identify oxidising and reducing agents.

Syllabus
2026–2028
Course
Chemistry 0620

Exam points

  • identify a reducing agent when acidified manganate(VII) changes from purple to colourless
  • identify an oxidising agent when iodide solution changes from colourless to brown iodine
  • state the acidic condition for the manganate(VII) test
  • report both start and end colours accurately in qualitative redox tests

CAIE IGCSE Chemistry 6.4.10 Redox Reactions By the Colour Changes Questions question 1

[Maximum number: 1]

Hydrogen iodide is dissolved in water.

HI→H++I−\mathrm{HI} \rightarrow \mathrm{H}^{+}+\mathrm{I}^{-}

Which row describes the final colours seen when the solution is tested with damp red litmus paper and with acidified aqueous potassium manganate(VII)?

damp red
litmus paper

acidified aqueous potassium
manganate(VII)

blue

brown

blue

colourless

red

brown

red

colourless

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