The chemical formula of Mohr salt is (NH4)2Fe(SO4)2.6H2O
We are given:
Concentration of mohr salt is mole of mohr saltvolume(L)
=3.92/392100/1000M=0.1M
Now, the chemical equation for the ionization of mohr salt follows:
(NH4)2Fe(SO4)2.6H2O→2NH+4+Fe2++2SO2−4+6H2O
From the equation,
we can say that the concentration of sulfate ions =(2×0.1)=0.2M
Option C is the correct answer.