Mohrs salt is used as a Primary standard in the permanganometric titrations because

Options

A. Mohrs salt has higher molecular weight than `FeSO_(4)` solution
B. `FeSO_(4)` is oxidised by air, where as Mohrs salt is stable
C. In Mohrs salt, the sulphate is also oxidized by `KMnO_(4)`
D. Mohrs salt is more soluble in water than `FeSO_(4)`

Answer

B

Explanation

`FeSO_(4).7H_(2)O,Fe^(2+)` is oxidised to `Fe^(3+)` by aerial `O_(2)`. In Mohr's salt `[FeSO_(4).(NH_(4))_(2)SO_(4)6H_(2)O],Fe^(2+)` is not oxidized to `Fe^(3+)`
`underset((r))(K_(2)Cr_(2)O_(7))overset(NH_(4)^((U))Cl+Con.H_(2)SO_(4))(rarr)underset(("Red gas")(V))(CrO_(2)Cl_(2))overset(NaOH+AgNO_(3))(rarr)`