MHT CET · Chemistry · Electrochemistry

Calculate the amount of electricity required to convert 1.1 mol of \(\mathrm{Cr}_2 \mathrm{O}_7^{2-}\) to \(\mathrm{Cr}^{+3}\) in acidic medium.

A \(6.369 \times 10^5 \mathrm{C}\)
B \(1.462 \times 10^5 \mathrm{C}\)
C \(4.839 \times 10^5 \mathrm{C}\)
D \(3.419 \times 10^5 \mathrm{C}\)

Verified Solution

Answer & Solution

Correct Answer

(A) \(6.369 \times 10^5 \mathrm{C}\)

Step-by-step Solution

Detailed explanation

\(14 \mathrm{H}^{+}+\mathrm{Cr}_2 \mathrm{O}_7^{2-}+6 \mathrm{e}^{-} \longrightarrow 2 \mathrm{Cr}^{3-}+7 \mathrm{H}_2 \mathrm{O}\) 1 mole of \(\mathrm{Cr}_2 \mathrm{O}_7^{2-}\) gets reduced by 6 moles of electrons to give 2 moles of \(\mathrm{Cr}^{3+}\).
\(\therefore 1.1 \text { mole of } \mathrm{Cr}_2 \mathrm{O}_7{ }^{2-}=6 \times 1.1=6.6 \text { moles of } \mathrm{e}^{-} \)
\( 1 \text { mole of electrons }=96500 \mathrm{C} \text { of electricity } \)
\( \therefore 6.6 \text { moles of electrons } \)
\( =6.6 \times 96500 \mathrm{C}=6.369 \times 10^5 \mathrm{C}\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Explore more questions on app

From MHT CET

Explore more questions on app