COMEDK 2024 Shift 2 Paper

To identify the compound W , let's examine the given reactions step by step:
1. The first reaction is:
W+‌

Na2CO3

O2∕‌ heat ‌

⟶X
This reaction involves an inorganic compound W being treated with sodium carbonate and oxygen under heat to form a compound X . This is a classic method employed to oxidize a compound. One known example is the oxidation of chromite ore where FeCr2O4 (chromite) gets oxidized to sodium chromate (Na2CrO4).
2. The second step:
X+H+⟶Y(s)
Adding acid H+ to sodium chromate (Na2CrO4) converts it to a solid dichromate compound. In aqueous solution, sodium chromate is converted to sodium dichromate ( Na2Cr2O7 ), which precipitates as a solid in a more concentrated solution.
3. The third reaction is:
Y(aq)+KCl(aq)⟶Z( s)
Here, when the resulting dichromate solution reacts with potassium chloride (KCl), potassium dichromate (K2Cr2O7) forms as a precipitate. Potassium dichromate is known for its orange crystals and is widely used as an oxidizing agent in acidic medium.
Based on these reactions, we can see the transformation of chromite FeCr2O4 into K2Cr2O7 through intermediates.
Thus, the compound W is:
Option B: FeCr2O4