Question

In acidic medium, which of the following does not change its colour?

• A. \( \text{MnO}_4^- \)
• B. \( \text{MnO}_4^{2-} \)
• C. \( \text{CrO}_4^{2-} \)
• D. \( \text{FeO}_4^{2-} \)

Hint:

In acidic conditions, \( \text{MnO}_4^- \) is stable and retains its purple colour, making it a reliable indicator in redox reactions.