Question

when a FeCr2O4 is fused with na2co3 in the presence of air it gives a yellow solution of compound a compound a on acidification gives compound b compound b on reaction with KCl forms an orange coloured compound c and acidified solution of compound c oxidises na2so3. Identify a b c and d

Answer 1

Answer:

a is red b is blue c is green d is purple

Answer 2

A is Na₂CrO₄.

B is Na₂Cr₂O₇

C is K₂Cr₂O₇

When fused chromite (FeCr₂O₄) is reacted with sodium carbonate (Na₂CO₃), sodium chromate (Na₂CrO₄) is formed,which is yellow in colour.

4FeCr₂O₄ +8 Na₂CO₃+ 7O₂ →8 Na₂CrO₄ + 2Fe₂O₃ + 8CO₂

So, A is Na₂CrO₄.

When Na₂CrO₄ is acidified in presence of H₂SO₄, sodium dichromate is formed (Na₂Cr₂O₇) along with sodium sulphate (Na₂SO₄) and H₂O.

2Na₂CrO₄ + H₂SO₄ → Na₂Cr₂O₇ + Na₂SO₄ + H₂O

Na₂Cr₂O₇ on reaction with KCl forms potassium dichromate (K₂Cr₂O₇).

Na₂Cr₂O₇ + 2KCl → K₂Cr₂O₇ + 2NaCl

K₂Cr₂O₇ formed is purple in colour.

So, B is Na₂Cr₂O₇ and C is K₂Cr₂O₇.

Acidic solution of K₂Cr₂O₇ oxidises Na₂SO₃ to Na₂SO₄.