CBSE Class 12 Chemistry 2019 Outside Delhi Set 2 Solved Paper

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Question : 6
Total: 27
SECTION - B

When 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). An acidified solution of compound (C) oxidises Na2SO3 to (D). Identify (A), (B), (C) and (D).
Solution:  
4FeCr2O4+8Na2CO3+7O2
8Na2CrO4+8Fe2O3+8CrO2
[A]

2Na2CrO4+2H+
Na2Cr2O7+2Na++H2O
[B]

Na2Cr2O7+2KCl
K2Cr2O7+2NaCl
[C]

K2Cr2O7+3Na2SO3+4H2SO4
3Na2SO4+K2SO4+Cr2(SO4)3+4H2O
[D]

[A] Na2CrO4 : Sodium chromate, [B]Na2Cr2O7. : Sodium dichromate, [C] K2Cr2O7 : Potassium dichromate, [D]Na2SO4 : Sodium sulphate.
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