Iron (III) catalyses the reaction between iodide and persulphate ions, in which

A. $$\mathrm{Fe}^{3+}$$ oxidises the iodide ion

B. $$\mathrm{Fe}^{3+}$$ oxidises the persulphate ion

C. $$\mathrm{Fe}^{2+}$$ reduces the iodide ion

D. $$\mathrm{Fe}^{2+}$$ reduces the persulphate ion

Choose the most appropriate answer from the options given below:

Arrange the following elements in the increasing order of number of unpaired electrons in it.

(A) $$\mathrm{Sc}$$

(B) $$\mathrm{Cr}$$

(C) $$\mathrm{V}$$

(D) $$\mathrm{Ti}$$

(E) $$\mathrm{Mn}$$

Choose the correct answer from the options given below :

The number of element from the following that do not belong to lanthanoids is $$\mathrm{Eu}, \mathrm{Cm}, \mathrm{Er}, \mathrm{Tb}, \mathrm{Yb}$$ and $$\mathrm{Lu}$$

While preparing crystals of Mohr's salt, dil $$\mathrm{H}_2 \mathrm{SO}_4$$ is added to a mixture of ferrous sulphate and ammonium sulphate, before dissolving this mixture in water, dil $$\mathrm{H_2SO_4}$$ is added here to :