Redox Exam-style MCQs | A-Level Chemistry OCR

Question 1

In which reaction is hydrogen acting as an oxidising agent?

Cl₂ + H₂➔ 2HCl

(CH₃)₂CO + H₂ ➔ (CH₃)₂CHOH

N₂ + 3H₂ ➔ 2NH₃

2Na + H₂ ➔ 2NaH

Question 2

Which is a redox reaction?

Cr₂O₇^2- + 2C ➔ Cr₂O₃ + CO₃^2- + CO

CrO₂Cl₂ + 4OH^- ➔ CrO₄^2- + 2Cl^- + 2H₂O

Cr₂O₇^2- + 2HCl ➔ 2CrO₃Cl^- + H₂O

2CrO₄^2- + 2H⁺ ➔ Cr2O₇^2- + H₂O

Question 3

The reaction between acidified dichromate(VI) ions, Cr₂O₇^2-, and aqueous Fe²⁺ ions results in the dichromate(VI) ions being reduced to Cr³⁺ ions.

What is the correct equation for this reaction?

Cr₂O₇^2- + Fe²⁺ + 14H⁺ ➔ 2Cr³⁺ + Fe³⁺ + 7H₂O

Cr₂O₇^2- + 2Fe²⁺ + 14H⁺ ➔ 2Cr³⁺ + 2Fe³⁺ + 7H₂O

Cr₂O₇^2- + 3Fe²⁺ + 14H⁺ ➔ 2Cr³⁺ + 3Fe³⁺ + 7H₂O

Cr₂O₇^2- + 6Fe²⁺ + 14H⁺ ➔ 2Cr³⁺ + 3Fe³⁺ + 6H₂O

Question 4

A solution of potassium manganate(VII) was used to determine the concentration of iron(II) ions in solution by titration in the presence of excess dilute sulfuric acid.

With the potassium manganate(VII) in the burette, the end-point of the reaction is when the solution in the conical flask turns

colourless

pink

green

orange