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NCERT Class XII Chemistry
Chapter - Coordination Compounds
Questions with Solutions

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Question : 13
Total: 43
Aqueous copper sulphate solution (blue in colour) gives :
(i) a green precipitate with aqueous potassium fluoride and
(ii) a bright green solution with aqueous potassium chloride. Explain these experimental results.
Solution:  
(i) Aqueous CuSO4 solution contains [Cu(H2O)4]2+ ions whichimpart blue colour. When KF is added, H2O being weak field ligand canbe replaced by F‌–forming [CuF4]2– ions which impart green colour.
[Cu(H2O)4]2++4F−[F]→[CuF4]2−+4H2O
‌‌‌‌‌‌‌[From‌KF](Green‌ppt.)
(ii) When KCl is added, Cl‌–ligand replaces H2O forming [CuCl4]2– ionswhich has bright green colour.
[Cu(H2O)]2++4Cl−→[CuCl4]−6HO+4H2O
‌‌‌‌‌[From‌KCl](Brightgreen‌solution)
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