Iron becomes passive by ..................... due to formation of .....................

Highest oxidation state of manganese in fluoride is $+4$ $(MnF_4)$ but highest oxidation state in oxides is $+7$ $(Mn_2O_7)$ because $..........$

Match the formulas given in Column-$I$ with the type of oxide given in Column-$II$ and select the correct option:-

Column-$I$	Column-$II$
$A$. $Pb_3O_4$	$I$. Neutral oxide
$B$. $N_2O$	$II$. Acidic oxide
$C$. $Mn_2O_7$	$III$. Basic oxide
$D$. $Bi_2O_3$	$IV$. Mixed oxide

Explain the trends in $M^{2+}/M$ standard electrode potentials.

Fill in the blanks:
$(a)$ The only $Mn$ halide compound that shows an oxidation state of $+7$ is ........
$(b)$ The $E^{\ominus}_{M^{II}/M}$ value is maximum negative for ........ in the $3d$ series.
$(c)$ Between $Cr^{2+}$ and $Fe^{2+}$,the stronger reducing agent is ........

When $Cu^{2+}$ ion is treated with $KI$,a white precipitate is formed. Explain the reaction with the help of a chemical equation.