In an analytical standard titration procedure, exactly mole of aqueous potassium dichromate () is en — d and f Block Elements Chemistry Question
Question
In an analytical standard titration procedure, exactly $1$ mole of aqueous potassium dichromate ($K_2Cr_2O_7$) is entirely consumed to quantitatively oxidise an acidic solution of Iron(II) sulphate. Exactly how many complete moles of $Fe^{2+}$ ions are comprehensively oxidised to $Fe^{3+}$ by this single mole of dichromate?
💡 Solution & Explanation
The overall balanced ionic redox equation is: $Cr_2O_7^{2-} + 14H^+ + 6Fe^{2+} \rightarrow 2Cr^{3+} + 6Fe^{3+} + 7H_2O$. A single mole of dichromate requires exactly $6$ moles of electrons to fully reduce its two $Cr^{6+}$ atoms to $Cr^{3+}$. Because the oxidation of $Fe^{2+}$ to $Fe^{3+}$ releases exactly $1$ electron per ion, it strictly requires $6$ moles of $Fe^{2+}$ to satisfy the $6$ -electron demand of one mole of dichromate.