Which of the following has second ionisation potential less than expected
$Cr$
$Zn$
$V$
$Mo$
Why transition elements form a coloured compounds?
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 $25$ )
In which of these processes platinum is used as a catalyst
Assertion : Transition metals are good catalysts.
Reason : $V_2O_5$ or $Pt$ is used in the preparation of $H_2SO_4$ by contact process.
Which of the following sulphides is yellow in colour