WAEC Chemistry 2025 Objective — Question 8

Question 8 of 50 from the West African Examinations Council (WAEC) Chemistry 2025 Objective paper, with the correct answer and a full explanation.

If acidified K2Cr2O7 acts as an oxidizing agent, the colour changes from

A. orange to red
B. yellow to green
C. orange to greenCorrect
D. yellow to red

Explanation

The orange colour of K2Cr2O7 is due to the dichromate ion (Cr2O7^2-). During redox, it is reduced to Cr3+, which is green. So the colour changes from orange to green: Cr2O7^2- + 14H+ + 6e- -> 2Cr3+ + 7H2O.

Sign up free to unlock

Score tracking
Practice history
Saved questions
Progress dashboard
Personalized sessions
Weak-topic breakdown

…and/or go further with premium services and No Ads.

Create free account

More questions from Chemistry 2025 Objective More Chemistry past papers