Why ${\mathrm{Ti}}^{+4}$ complexes are diamagnetic?

A substance is found to have a magnetic moment of $3.9 \mathrm{BM}$. How many unpaired electrons does it contain?

Explain by giving reason.
(a) Transition metals and many of their compounds show paramagnetic behaviour.
(b) The enthalpies of atomisation of the transition metals are high.
(c) The transition metals generally form coloured compounds.

Why ${\mathrm{KMnO}}_4$ is stored in dark bottle and what happens to it's acidic solution?

Why it is not advisable to dissolve ${\mathrm{KMnO}}_4$ in cold and concentrated ${\mathrm{H}}_2{\mathrm{SO}}_4$?

What happens when :
(a) Green vitriol is strongly heated.
(b) Malachite is made to react with dilute ${\mathrm{H}}_2{\mathrm{SO}}_4$
(c) Copper sulphate is exposed to air for longer period.
(d) Lunar caustic is made to react with sodium hydroxide and then product is dried.
(e) Silver nitrate reacts with excess iodine.
(f) Potassium dichromate reacts with cold and concentrated ${\mathrm{H}}_2{\mathrm{SO}}_4$