The formula mass of Mohr's salt is 392. The iron present in it is oxidised by `KMnO_(4)` in acid medium. The equivalent mass of Mohr's salt is :

Options

A. 392
B. 31.6
C. 278
D. 156

Answer

A

Explanation

Formula of Mohr's salt: `FeSO_(4).(NH_(4))_(2)SO_(4).6H_(2)O`
Oxidation of `Fe^(2+)` ions take place as :
`5Fe^(2+) +MnO_(4)^(-)+8H^(+) to 5Fe^(3+) +Mn^(2+)+4H_(2)O`
Change in oxidation number of `Fe=+3-(+2)=+1`
Equivalent mass of Mohr's salt`=("Molecular mass")/("Change in oxidation number")`
`=(392)/(1)=392`