JEE Advance - Chemistry (2007 - Paper 2 Offline - No. 1)
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
3
4
5
6
Explanation
The formula of Mohr's salt is $$\mathrm{FeSO_4(NH_4)_2SO_4}$$. It is a mixture of ferrous sulfate and ammonium sulfate. Ferrous sulfate is oxidized by potassium dichromate to ferric sulphate.
Reaction is as follows:
$$\mathrm{K_2Cr_2O_7+6FeSO_4+7H_2SO_4\to K_2SO_4+Cr_2(SO_4)_3+3Fe_2(SO_4)_3+7H_2O}$$
1 mole of potassium dichromate reacts with 6 moles of ferrous sulphate. Thus, number of moles of Mohr's salt required per mole of dichromate is 6.
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