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Standard VII

Chemistry

Properties of Bases

A green colou...

Question

A green coloured chromium compound 'A' on fusion with alkali gives a yellow compound 'B' which on acidification gives an oragne compound 'C' which reacts with NH4Cl to form orange compound 'D' . 'D' on heating gives 'A' back . identify A,B,C,D and give reactions

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Solution

A - Cr₂O₃
B - K₂CrO₄
C - K₂Cr₂O₇
D - (NH₄)₂Cr₂O₇
CrO₃ + 2KOH â†’ K₂CrO₄ + H₂O
2K₂CrO₄ + H₂SO₄ â†’ K₂CrO₇ + K₂SO₄ + H₂O
K₂Cr₂O₇ + NH₄Cl â†’ (NH₄)₂Cr₂O₇ + 2KCl
(NH₄)₂Cr₂O₇ â†’ CrO₃ + N₂ + 4H₂O

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A green coloured chromium compound 'A' on fusion with alkali gives a yellow compound 'B' which on acidification gives an oragne compound 'C' which reacts with NH4Cl to form orange compound 'D' . 'D' on heating gives 'A' back . identify A,B,C,D and give reactions

A - Cr2O3B - K2CrO4C - K2Cr2O7D - (NH4)2Cr2O7CrO3 + 2KOH â†’ K2CrO4 + H2O2K2CrO4 + H2SO4 â†’ K2CrO7 + K2SO4 + H2OK2Cr2O7 + NH4Cl â†’ (NH4)2Cr2O7 + 2KCl(NH4)2Cr2O7 â†’ CrO3 + N2 + 4H2O

A - Cr₂O₃
B - K₂CrO₄
C - K₂Cr₂O₇
D - (NH₄)₂Cr₂O₇
CrO₃ + 2KOH â†’ K₂CrO₄ + H₂O
2K₂CrO₄ + H₂SO₄ â†’ K₂CrO₇ + K₂SO₄ + H₂O
K₂Cr₂O₇ + NH₄Cl â†’ (NH₄)₂Cr₂O₇ + 2KCl
(NH₄)₂Cr₂O₇ â†’ CrO₃ + N₂ + 4H₂O