Consider the following transformation $2 \ CuX_2 \xrightarrow[\text{Room}]{\text{temp.}} Cu_2X_2 + X_2 \uparrow$. Then $X^{-}$ can be:

Assertion $(A)$: $CuI_2$ cannot be prepared by the reaction of $Cu^{2+}_{(aq)}$ with $I^{-}_{(aq)}$.
Reason $(R)$: Aqueous $Cu^{2+}$ solution is blue in colour.
The correct answer is:

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

Explain the catalytic properties of transition metals.

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

Write the chemical reactions of lanthanoids $(Ln)$ with the following:
$(1)$ With acid:
$2Ln + 6HCl \rightarrow 2LnCl_3 + 3H_2$
$(2)$ With halogens ($X_2$,where $X = F, Cl, Br, I$):
$2Ln + 3X_2 \rightarrow 2LnX_3$