Urea reacts with water to form A which will decompose to form B. B when passed through $Cu^{2+}(aq)$, deep blu

Question

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

Accepted Answer

1.  **Formation of B:** Urea ($NH_2CONH_2$) on hydrolysis with water forms ammonium carbonate (A), which is unstable and decomposes to give ammonia ($NH_3$), water, and carbon dioxide.
    $$NH_2CONH_2 + 2H_2O ightarrow (NH_4)_2CO_3 ightarrow 2NH_3 + H_2O + CO_2$$
    Thus, compound **B is Ammonia ($NH_3$)**.
2.  **Formation of C:** When ammonia solution is added to aqueous copper(II) ions ($Cu^{2+}$), 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).
    $$Cu^{2+}(aq) + 4NH_3(aq) ightarrow [Cu(NH_3)_4]^{2+}(aq) 	ext{ (Deep Blue)}$$
    This complex is explicitly mentioned as an example of a coordination compound in the NCERT text .

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