The dand fblock elements - Result Question 54
####54. The addition of excess of aqueous $HNO_3$ to a solution containing $[Cu(NH_3)_4]^{2+}$ produces
[1999]
(a) $Cu^{+}$
(b) $[Cu(H_2 O)_4]^{2+}$
(c) $Cu(OH)_2$
(d) $Cu(NO_3)_2$
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Solution:
- (b) When excess of aq. $HNO_3$ to $[C_4(H_3)_4]^{2+}$ produces $[(4(H_2 O)_4]^{2+}.$.
Following equillibrium exist in the given aqueous solution
$[Cu(H_2 O)_4]^{2+}(aq)+4 NH_3(aq) \rightarrow$
$ [Cu(NH_3)_4]^{2+}(aq)+4 H_2 O(l) $
When $HNO_3$ is added to this solution:
(excess) $HNO_3$ (aq) $+NH_3$ (aq) $\longrightarrow$
$ NH_4^{+}(aq)+NO_3^{-}(aq) $
Thus, amount of $NH_3(aq)$ will reduce drastically. With a simple application of Le Chatelier’s principle, the equillibrium will shift towards left in the first reaction. Hence, $[Cu(H_2 O)_4]^{2+}$ will form.
