Question

The colour of \( \text{CrO}_4^{2-} \) changes to \( \text{Cr}_2\text{O}_7^{2-} \) is

• A. yellow to orange
• B. orange to yellow
• C. yellow to blue
• D. orange to blue

Hint:

The colour change from yellow to orange is a characteristic feature of the chromate-dichromate equilibrium in acidic solutions.

Answer 1

The Correct Option is A

Chromate ion \( \text{CrO}_4^{2-} \) is yellow in colour, and dichromate ion \( \text{Cr}_2\text{O}_7^{2-} \) is orange in colour. The transition from chromate to dichromate occurs in acidic medium, and the colour change is from yellow to orange. Thus, the correct answer is yellow to orange.