During the electrolysis of copper sulphate aqueous solution using copper electrode, the reaction takine…

During the electrolysis of copper sulphate aqueous solution using copper electrode, the reaction takine place at the cathode is
  1. $\mathrm{Cu} \longrightarrow \mathrm{Cu}^{2+}(\mathrm{aq})+2 e^{-}$
  2. $\mathrm{Cu}^{2+}(\mathrm{aq})+2 e^{-} \longrightarrow \mathrm{Cu}(\mathrm{s})$
  3. $\mathrm{H}^{+}(\mathrm{aq})+\mathrm{e}^{-} \longrightarrow \frac{1}{2} \mathrm{H}_2(g)$
  4. $\mathrm{SO}_4^{2-}(\mathrm{aq}) \longrightarrow \mathrm{SO}_3(g)+\frac{1}{2} \mathrm{O}_2(g)+2 e^{-}$

Solution

During the electrolysis of an aqueous solution of copper sulphate using copper electrodes, both $\mathrm{Cu}^{2+}$ and $\mathrm{H}^{+}$ions move towards cathode, but the discharge potential of $\mathrm{Cu}^{2+}$ ions is lower than that of $\mathrm{H}^{+}$ions, therefore $\mathrm{Cu}^{2+}$ ions are discharged in preference to $\mathrm{H}^{+}$ions and copper is deposited on the cathode. $ \mathrm{Cu}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Cu}(\mathrm{s}) \text { (at cathode) } $

Asked in: AP EAMCET 2013

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