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Urea reacts with water to form A which will decompose to form B. B when passed through Cu2+(aq)Cu^{2+}(aq), deep blue colour solution C is formed. What is the formula of C from the following?

A

[Cu(NH3)4]2+[Cu(NH_3)_4]^{2+}

B

Cu(OH)2Cu(OH)_2

C

CuCO3⋅Cu(OH)2CuCO_3 \cdot Cu(OH)_2

D

CuSO4CuSO_4

Step-by-Step Solution

  1. Formation of B: Urea (NH2CONH2NH_2CONH_2) on hydrolysis with water forms ammonium carbonate (A), which is unstable and decomposes to give ammonia (NH3NH_3), water, and carbon dioxide. NH2CONH2+2H2O→(NH4)2CO3→2NH3+H2O+CO2NH_2CONH_2 + 2H_2O \rightarrow (NH_4)_2CO_3 \rightarrow 2NH_3 + H_2O + CO_2 Thus, compound B is Ammonia (NH3NH_3).
  2. Formation of C: When ammonia solution is added to aqueous copper(II) ions (Cu2+Cu^{2+}), the water ligands are replaced by ammonia ligands (which are stronger field ligands in the spectrochemical series relative to water, though closer in strength, ammonia forms stable amine complexes). This results in the formation of a deep blue complex ion, tetraamminecopper(II). Cu2+(aq)+4NH3(aq)→[Cu(NH3)4]2+(aq) (Deep Blue)Cu^{2+}(aq) + 4NH_3(aq) \rightarrow [Cu(NH_3)_4]^{2+}(aq) \text{ (Deep Blue)} This complex is explicitly mentioned as an example of a coordination compound in the NCERT text .
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