The colour imparted by $Co(II)$ compounds to glass is

Which of the following statements regarding copper salts is not true?

Which of the following is the correct formula for a compound of scandium and oxygen?

$Fe_2Cr_2O_4 + Na_2CO_3 + O_2$ $\xrightarrow{\text{Fusion}} [X]$ $\xrightarrow[H_2O]{H^{+}} [Y]$ $\xrightarrow{H_2O_2/H^{+}} [Z]$
Which of the following statements is true for the compounds $[X]$,$[Y]$,and $[Z]$?

Chromite ore $\xrightarrow{Na_2CO_3 + O_2} A$ $\xrightarrow[NaOH]{H_2SO_4} B$. Which of the following is correct?

Indicate the steps in the preparation of:
$(i)$ $K_2Cr_2O_7$ from chromite ore.
$(ii)$ $KMnO_4$ from pyrolusite ore.