When chromite ore FeCr_(2)O_(4) 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 ) .

When chromite ore FeCr_(2)O_(4) is fused with NaOH in presence of air,

1.	When chromite ore FeCr_(2)O_(4) 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 ) .
Answer» Solution :(i) `4FeCr_(2)O_(4) + 16 NaOH + 7O_(2) RARR underset("(A)(Sodium chromate")(8 Na_(2)CrO_(4))+ 2Fe_(2)O_(3)+ 8 H_(2)O` `2Na_(2)CrO_(4) + H_(2)SO_(4) rarr underset("(B) Sodium dichromate")(Na_(2) Cr_(2)O_(7)) + Na_(2)SO_(4)+ H_(2)O` `Na_(2)Cr_(2)O_(7) + 2KCl rarr underset("(C ) Potassium dichromate")( K_(2)Cr_(2) O_(7)) + 2NaCl` (ii)Potassium dichromate is used as a powerful oxidizing agent in industriesand in the tanning of leather.