$K_2Cr_2O_7$ paper acidified with dilute $H_2SO_4$ turns green when exposed to

In the following reactions $(i)$ $MnO_2 + 4 HCl \rightarrow$ and $(ii)$ $2 KMnO_4 + 16 HCl \rightarrow$,the number of moles of chlorine gas released respectively are

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

In the reaction,$4Fe + 3O_2 \to 4Fe^{3+} + 6O^{2-}$,which of the following statements is incorrect?

Assign $A, B, C, D$ from the given type of reaction.
$K_2Cr_2O_7 + 2NaOH \longrightarrow 2K_2CrO_4 + H_2O$
Identify the nature of the product $CrO_4^{2-}$ formed in the reaction.

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$Na_2CrO_4 + AgF \longrightarrow Ag_2CrO_4 \downarrow + NaF$