What are the impurities present in ruby and sapphire?

Write a note on halide compounds of transition elements.

Which compound of zinc is white in the cold state and turns yellow in the hot state?

For $Cu_{2}Cl_{2}$ and $CuCl_{2}$ in aqueous medium,which of the following statements is correct?

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

Match List-$I$ with List-$II$:

List-$I$ (Transition metal/Compound/complex)	List-$II$ (Catalytic Role)
$A$. $V_2O_5$	$I$. Preparation of ammonia from $N_2/H_2$ mixture
$B$. $Fe$	$II$. Polymerisation of alkynes
$C$. $PdCl_2$	$III$. Preparation of $H_2SO_4$ from $SO_2$
$D$. $Ni$ complex	$IV$. Oxidation of ethyne to ethanal