Which of the following statements about the titration of Fe^2+ with acidified K2Cr2O7 are correct?

The orange colour of dichromate changes to green (Cr^3+) as it is reduced.

The equivalent mass of K2Cr2O7 is one-sixth of its molar mass.

The orange colour of dichromate changes to green (Cr^3+) as it is reduced.

One mole of K2Cr2O7 accepts three moles of electrons.

Potassium dichromate is a self-indicator, so no indicator is needed.

The equivalent mass of K2Cr2O7 is one-sixth of its molar mass.

MolSynapse / Question bank / Equivalent Concept and Titration / Redox titrations with KMnO4 and K2Cr2O7

JEE Main levelOne or more correct optionsDifficulty 2 of 3eq063

Which of the following statements about the titration of $Fe X^{2 +}$ with acidified $K X_{2} Cr X_{2} O X_{7}$ are correct?

AThe orange colour of dichromate changes to green ( $Cr X^{3 +}$ ) as it is reduced.
BOne mole of $K X_{2} Cr X_{2} O X_{7}$ accepts three moles of electrons.
CPotassium dichromate is a self-indicator, so no indicator is needed.
DThe equivalent mass of $K X_{2} Cr X_{2} O X_{7}$ is one-sixth of its molar mass.

Answer: A, D

Two Cr(VI) go to Cr(III), taking 6 electrons per formula unit, so the equivalent mass is M/6 and the colour changes from orange to green. Dichromate is not a self-indicator (the green Cr3+ masks the end point, so an internal redox indicator such as diphenylamine is used), and it accepts 6, not 3, electrons per mole. Correct: first and second.

Practice Equivalent Concept and Titration More on Redox titrations with KMnO4 and K2Cr2O7

Previous questionNext question

Which of the following statements about the titration of FeX2+ with acidified KX2​CrX2​OX7​ are correct?

Answer: A, D

More questions on Redox titrations with KMnO4 and K2Cr2O7

Which of the following statements about the titration of $Fe X^{2 +}$ with acidified $K X_{2} Cr X_{2} O X_{7}$ are correct?