Which of the following decolourises the colour of acidic $KMnO_4$?

$10 \, \text{mole}$ of ferric oxalate is oxidised by $x \, \text{mole}$ of $MnO_4^-$ in acidic medium. The value of $x$ is

The autocatalyst in the redox reaction involving acidified potassium permanganate and oxalic acid is

Consider the following redox reaction in basic medium.
$x \ Cr(OH)_3 + y(IO_3)^{-} + z(OH)^{-} \rightarrow a(CrO_4)^{2-} + b(I)^{-} + c(H_2O)$
The incorrect option about it is

Upon the addition of a solution $A$ to a strongly acidified solution of barium nitrate,a white precipitate was obtained which did not dissolve even after large addition of water. Solution $A$ contained

Metal sulphate $(A) \xrightarrow{\text{Heat}}$ Oxide $(B) +$ Gas $(C) +$ Gas $(D) \xrightarrow{Cr_2O_7^{2-} / H^{+}}$ Green solution $\xrightarrow[\text{Excess}]{Na_2O_2}$ Yellow solution $(E)$. Compound $A, B, C, D$ and $E$ are respectively: