When chromite ore `FeCr_(2)O_(4)` is fuse with NaOH in presence of air, a yellow coloured compound (A) is obtained which on acidification with dilute sulphuric acid gives a compound (B). Compound (B) on reaction with KCl formas an orange colured crystalline compound (C).
(i) Write the formulae of the compounds (A),(B) and (C).
(ii) Write one use of compounds (C).

When chromite ore FeCr_(2)O_(4) is fuse with NaOH in presence of air, a yellow coloured compound (A) is obtained which on acidification with dilute sulphuric acid gives a compound (B). Compound (B) on reaction with KCl forms an orange coloured crystalline compound (C). (i) Write the formula of the compounds (A),(B) and (C). (ii) Write one use of compounds (C).

(a) When a chromite ore (A) is fused with an aqueous solution of sodium carbonate in free excess of air, a yellow solution of compound (B) is obtained. This solution is filtered and acidified with sulphuric acid to form compound (C). Compound (C) on treatment with solution of KCl gives orange crystals of compound (D). Write the chemical formulae of compounds A to D. (b) Describe the cause of the following variations with reSQPect to lanthanoids and actinoids: (i) Greater range of oxidation states of actinoids as compared to lanthanoids. (ii) Greater actinoid contraction as compared to lanthanoid contraction. (iii) Lower ionisation enthalpy of early actinoids as compared to the early lanthanoids.

A mixed oxide of iron and chromium, FeO.Cr_2O_3 is fused with sodium carbonate in the presence of air to form a yellow compound (A). On acidification, the compound (A) forms an orange coloured compound (B) which is a strong oxidising agent. Identify (i) the compounds (A) and (B) (ii) write balanced chemical equations for each step.