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

Correct Answer is : orange to green

Correct Answer is : orange to green

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WAEC Chemistry 2025 Paper

Question : 8

Total: 50

If acidified K

_2

_2

_7

acts as an oxidizing agent, the colour changes from

Solution:

Concept:

Acidified

\mathrm{K}_2\mathrm{Cr}_2\mathrm{O}_7

changes colour when it is reduced during an oxidation–reduction reaction.

Explanation:

In acidic solution, the dichromate ion,

\mathrm{Cr}_2\mathrm{O}_7^{2-}

, has an orange colour.

When it acts as an oxidizing agent, it accepts electrons and is reduced.

The chromium in

\mathrm{Cr}_2\mathrm{O}_7^{2-}

is in the

+6

oxidation state.

After reduction, it forms

\mathrm{Cr}^{3+}

ions, which have a green colour in aqueous solution.

Hence, the observed colour change is from orange to green.

Answer:

C. orange to green

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