When chromite ore FeCr₂O₄ is fused 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 formulae of the compounds (A), (B) and C.
(ii)Write one use of compound (C).
                                  
                                                OR