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:
(The formula for Mohr's salt is FeSO4.(NH4)2SO4.6H2O)
A
6
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
B
5
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
4
No worries! We‘ve got your back. Try BYJU‘S free classes today!
D
3
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution
The correct option is A 6 Mohr's salt≡FeSO4.(NH4)2SO4.6H2O
Dichromate will oxidise Fe2+ from Mohr's salt to Fe3+.
+6Cr2O2−7++2Fe2+H+⟶+3Cr3+++3Fe3+
nf=(|Change in O.S.|)×Number of atoms nfCr2O2−7=|+3−(+6)|×2=6 nfFe2+=|+3−(+2)|×1=1
From the law of equivalence, Equivalents of Fe2+=Equivalents of Cr2O2−7 nFe2+×1=1×6 ∴nMohr's salt=nFe2+=6mol