How many moles of Fe^2+ are oxidised to Fe^3+ by one mole of Cr2O7^2- in acidic solution?

JEE Main levelSingle correct optionDifficulty 2 of 3df090

How many moles of $Fe X^{2 +}$ are oxidised to $Fe X^{3 +}$ by one mole of $Cr X_{2} O X_{7} X^{2 -}$ in acidic solution?

Cr X_{2} O X_{7} X^{2 -} + 14 H X^{+} + 6 e^{-} \to 2 Cr X^{3 +} + 7 H X_{2} O

takes up 6 electrons (two Cr from

+ 6

+ 3

), and each

Fe X^{2 +}

gives one electron, so 6 mol

Fe X^{2 +}

react.