The crystal field theory is successful in explaining which of the following?

I. Ligands as point charges.

II. Formation and structures of complexes.

III. Colour.

IV. Magnetic properties.

V. Covalent character of metal-ligand bonding.

Which of the following is correct related to the colours of $$\mathrm{TiCl}_3(X)$$ and $$\left[\mathrm{Ti}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right] \mathrm{Cl}_3(Y)$$ ?

$$\mathrm{AlF}_3$$ is soluble in HF only in the presence of KF due to formation of

Potassium cyanide is made alkaline with NaOH and boiled with thiosulphate ions. The solution is cooled and acidified with HCl and this solution with iron (III) chloride produces