One of the important uses of ferrous sulphate is in the

Given below are two statements:
Statement $I :$ Potassium permanganate on heating at $573 \ K$ forms potassium manganate.
Statement $II :$ Both potassium permanganate and potassium manganate are tetrahedral and paramagnetic in nature.
In the light of the above statements,choose the most appropriate answer from the options given below.

Which of the following statements is not true?

Identify the correct $(T)$ and incorrect $(F)$ statements from the following:
$(a)$ $MnO_4^{2-}$ is diamagnetic.
$(b)$ $MnO_4^-$ is green and $MnO_4^{2-}$ is purple.
$(c)$ $K_2Cr_2O_7$ is yellow.
$(d)$ $K_2Cr_2O_7$ is orange.

Correct statements from the following are:
$A$. Potassium dichromate is an oxidising agent and it oxidises $FeSO_4$ to $Fe_2(SO_4)_3$ in acidic medium.
$B$. Sodium dichromate can be used as primary standard in volumetric estimation.
$C$. $CrO_4^{2-}$ and $Cr_2O_7^{2-}$ are interconvertible in aqueous solution by varying the $pH$ of the solution.
$D$. $Cr-O-Cr$ bond angle in $Cr_2O_7^{2-}$ is $126^\circ$.
Choose the correct answer from the options given below:

Provide the structures for:
$1.$ $MnO_4^{-}$
$2.$ $MnO_4^{2-}$