Which of the following metals becomes passive when treated with concentrated $HNO_3$?

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:

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 $X = F, Cl, Br, I$):
$2Ln + 3X_2 \rightarrow 2LnX_3$

Which of the following orders is not correct?

At $pH = 12$,what change occurs in $Cr_2O_7^{2-}$?

The order of basic character for the monoxides of transition metals is . . . . .