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Questions
Explain why Cu+ ion is not stable in aqueous solutions?
Out of Cu+ and Cu2+, which ion is unstable in aqueous solution and why?
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Solution
\[\ce{Cu^{2+}_{ (aq)}}\] is more stable than \[\ce{Cu^{+}_{ (aq)}}\]. This is because copper has a higher second ionization enthalpy, but ΔhydH for \[\ce{Cu^{2+}_{ (aq)}}\] is more negative than that for \[\ce{Cu^{+}_{ (aq)}}\], so it compensates more for the second ionization enthalpy of copper. Thus many copper (I) compounds are unstable in aqueous solution and are disproportionated as follows:
\[\ce{2Cu^{+}_{ (aq)} -> Cu^{2+}_{ (aq)} + Cu_{(s)}}\]
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