Litharge is chemically

Which of the following statements are correct about the reaction between the copper metal and dilute $HNO_3$?
$(I)$ The principal reducing product is $NO$ gas.
$(II)$ $Cu$ metal is oxidised to $Cu^{2+}$ (aq.) ion which is blue in colour.
$(III)$ $NO$ is paramagnetic and has one unpaired electron in antibonding molecular orbital.
$(IV)$ $NO$ reacts with $O_2$ to produce $NO_2$ which is linear in shape.
Choose the correct statements.

In the Ostwald process for the manufacture of $HNO_3$,which of the following is used as a catalyst?

When bismuth chloride is poured into a large volume of water,the white precipitate produced is

In some of the reactions,thallium resembles aluminium,whereas in others,it resembles group $1$ metals. Support this statement by giving some evidence.

$Ge(II)$ compounds are powerful reducing agents whereas $Pb(IV)$ compounds are strong oxidants. This can be attributed to: