$ \uparrow Y_{(g)} \xleftarrow{KI} CuSO_4 \xrightarrow{dil. H_2SO_4} X (\text{Blue colour}) $. $X$ and $Y$ are:

Fusion of $MnO_2$ with $KOH$ in the presence of air or an oxidizing agent like $KNO_3$ forms a colored compound. Identify the product and its color.

The fusion of chromite ore $(FeCr_{2}O_{4})$ with $Na_{2}CO_{3}$ in air gives a yellow solution upon addition of water. Subsequent treatment with $H_{2}SO_{4}$ produces an orange solution. The yellow and orange colours,respectively,are due to the formation of

In the scheme given below,$X$ and $Y$,respectively,are:
$\text{Metal halide} \xrightarrow{\text{aq. NaOH}} \text{White precipitate } (P) + \text{Filtrate } (Q)$
$P \xrightarrow[\text{heat}]{\text{aq. } H_2SO_4, PbO_2 (\text{excess})} X (\text{a coloured species in solution})$
$Q$ $\xrightarrow[\text{warm}]{\text{MnO(OH)}_2, \text{Conc. } H_2SO_4} Y (\text{gives blue-coloration with KI-starch paper})$

Assertion : Solution of $Na_2CrO_4$ in water is intensely coloured.
Reason : Oxidation state of $Cr$ in $Na_2CrO_4$ is $+VI$.

Fill in the blanks:
$(1)$ Since $V_2O_5$ acts as both an acid and a base,it is an ...... oxide.
$(2)$ The $Cr$ oxide which is basic is ......,and the $Cr$ oxide which is amphoteric is ...... .
$(3)$ The formula of chromite ore is .......... .
$(4)$ The formula of sodium dichromate crystal is .......... .