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A mixed oxide of iron and chromium FeO.C...

A mixed oxide of iron and chromium `FeO.Cr_(2)O_(3)` is fused with sodium carbonate in the presence of air to form a yellow coloured compound (A). On acidification , the compound (A) forms an orange coloured compound (B) which is a strong oxidising agent. Identify (i) the compound A and B (ii) Write balanced chemical equation for each step.

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The mixed oxide `FeO.Cr_(2)O_(3)` is the chromatic ore of iron also called ferro-chrome. It is written as `FeCr_(2)O_(4)`. Upon fusing with sodium carbonate in the presence of air, it give as yellow compound (A) which is sodium chromate. .
`2FeCr_(2)O_(4)+8Na_(2)CO_(3)+underset((Air))(7O_(2)) overset("Fuse") to underset("(Yellow)")underset("Sod. chromate (A)")(8Na_(2)CrO_(4))+2Fe_(2)O_(3)+8CO_(2)`
Sodium chromate (A) upon acidification with concentrated sulphuric acid changes to sodium dichromate (B) which has an orange colour.
`underset("Sod.chromate")(2Na_(2)CrO_(4))+H_(2)SO_(4) to underset("(orange)")underset("Sod. dichromate (B)")(Na_(2)Cr_(2)O_(7))+Na_(2)SO_(4)+H_(2)O`
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