When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, Compound (C ) can be crystallised from the solution. When compound (C ) is treated with KCl, orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.

When a chromite ore (A) is fused with sodium carbonate in free excess

1.	When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, Compound (C ) can be crystallised from the solution. When compound (C ) is treated with KCl, orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.
Answer» Solution :`A: FeCr_(2)O_(4), B: Na_(2)CrO_(4)` `C: Na_(2) Cr_(2)O_(7), D: K_(2)Cr_(2)O_(7)` `underset((A))(4FeCr_(2)O_(4)) + 8Na_(2)CO_(3) + 7O_(2) rarr underset((B))(8Na_(2)CrO_(4))` `underset((B))(2Na_(2)CrO_(4)) + 2H^(+) rarr Na_(2)Cr_(2)O_(7) + H_(2)O + 2NA^(+)` `underset((C ))(Na_(2)Cr_(2)O_(7)) + 2KCl rarr underset((D))(K_(2)Cr_(2)O_(7)) + 2NaCl`