Amphoteric oxide$(s)$ of $Mn$ is/are:

The fusion of manganese dioxide with $KOH$ in the presence of an oxidizing agent like $KNO_3$ yields a compound. Identify the compound and its color.

The conversion of pig iron to steel frequently requires the addition of
$(I)$ oxygen or iron oxide
$(II)$ transition elements
$(III)$ inner transition elements
$(IV)$ silica

Potassium dichromate when heated with concentrated sulphuric acid and a soluble chloride,gives brown-red vapours of:

Which from the following alloys is used in gas turbine engines?

The orange-red color of an aqueous solution of $K_2Cr_2O_7$ changes to lemon yellow when treated with aqueous $KOH$. What is the reason for this?