Waec Model Questions Vol1 2021 Chemistry Question 21

Practice objective / multiple choice question 21 from the 2021 Waec Model Questions Vol1 Chemistry examination.

Waec Model Questions Vol1 2021 Chemistry Objective / Multiple Choice Medium Difficulty
Question 21 WAEC_MODEL_QUESTIONS_VOL1 • 2021 • CHEMISTRY • objective

A 200.0 mL solution contains Fe²⁺ and Cr²⁺ ions. It is titrated with 0.0200 M KMnO₄ in acidic medium. Exactly 25.0 mL of the KMnO₄ solution is added, which first oxidises all Fe²⁺ and then partially oxidises Cr²⁺. The excess KMnO₄ remaining after the reaction is back‑titrated with 0.0100 M Fe²⁺ solution, requiring 10.0 mL. If the original concentration of Cr²⁺ was 0.0050 M, calculate the original concentration of Fe²⁺ in the mixture.

Answer Options

A. 5.0×10⁻³ M
Correct Answer B. 7.0×10⁻³ M
C. 7.0×10⁻² M
D. 9.0×10⁻³ M
Correct Answer
B
Correct Option:
7.0×10⁻³ M

About This Question

This is Waec Model Questions Vol1 2021 Chemistry Question 21. It is a objective / multiple choice question from the 2021 Waec Model Questions Vol1 Chemistry examination.

Difficulty level: Medium .

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