IIT-JEE 2007 · Paper 2 · Chemistry Q23

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ChemistrySingle correct+3 / -1Question 23 of 66

Consider a titration of potassium dichromate solution with acidified Mohr's salt solution using diphenylamine as indicator. The number of moles of Mohr's salt required per mole of dichromate is

Answer and worked solution

Official answer: D

Half-reactions. $\ce{Cr2O7^{2-} + 14H+ + 6e- -> 2Cr^{3+} + 7H2O}$ , and each $\ce{Fe^{2+}}$ (from Mohr's salt) gives one electron.

So one mole of dichromate oxidises 6 mol of $\ce{Fe^{2+}}$ , i.e. 6 mol of Mohr's salt.

(D)

Topics:Redox titrations Important compounds (KMnO4, K2Cr2O7)

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IIT-JEE 2007 · Paper 2, Chemistry question 23