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Edexcel A-Level Chemistry A2 17.21 Dichromate Vi Ions Can Be Converted Into Chromate Vi Ions Through the Equilibrium Cr2o7 2 H2o 2cro4 2 2h Questions

Use the equilibrium equation to explain the colour: alkali removes H+ and favours yellow chromate(VI), while acid favours orange dichromate(VI).

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
A2

Exam points

  • Explain alkaline shift to chromate(VI) by removal of H+ from equilibrium.
  • Write 2CrO4^2- plus 2H+ forming Cr2O7^2- and water for acidification equations.
  • Identify yellow chromate(VI), orange dichromate(VI) and green chromium(III) species.

Edexcel A-Level Chemistry A2 17.21 Dichromate Vi Ions Can Be Converted Into Chromate Vi Ions Through the Equilibrium Cr2o7 2 H2o 2cro4 2 2h Questions question 1

[Maximum number: 1]

Solution A and solution B are aqueous solutions.
The compound in each solution contains one cation and one anion.
The cations are different but the anions are the same.
Both solutions are green.

The student added hydrogen peroxide solution to C and warmed the mixture, which turned yellow. The yellow solution was boiled to remove excess hydrogen peroxide, cooled and then pure ethanoic acid was added, drop by drop. The yellow solution gradually turned orange.

Identify, by name or formula, the ion responsible for the final orange colour of the solution.

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