Properties common to the elements manganese, iron, cobalt, nickel and copper include the ready formation by them all of

$(I)$ coloured ions in aqueous solution

$(II)$ oxides of nitrogen are formed on reaction with concentrated $HNO_3$

$(III)$ chlorides of formula $MCl_2$ and $MCl_3$

Consider the following reaction

$\mathrm{MnO}_2+\mathrm{KOH}+\mathrm{O}_2 \rightarrow \mathrm{A}+\mathrm{H}_2 \mathrm{O} .$

Product ' $A$ ' in neutral or acidic medium disproportionate to give products ' $\mathrm{B}$ ' and ' $\mathrm{C}$ ' along with water. The sum of spin-only magnetic moment values of $B$ and $C$ is . . . . . .$BM$. (nearest integer)

(Given atomic number of $\mathrm{Mn}$ is $25$ )

Which of the following ions has the maximum magnetic moment

In a reaction the ferrous $(F{e^{ + 2 }})$ iron is oxidised to ferric $(F{e^{ + 3 }})$ ion. The equivalent weight of the ion in the above reaction is equal to

In first transition series, the melting point of $Mn$ is low because

Metre scales are made-up of alloy