Question

Predict the products of electrolysis in an aqueous solution of ${\mathrm{CuCl}}_2$ with platinum electrodes.

Answer 1

Electrolysis:

• Electrolysis is a process by which electrical energy is used to produce a chemical change.
• The electrolysis cell consists of two metallic rods known as electrodes that are connected to a battery and dipped into molten electrolyte or electrolyte solution.
• The electrode connected to the positive side of the battery is called the anode.
• The electrode connected to the negative side of the battery is called the cathode.
• The electrically charged cations and anions present in the electrolyte move towards the respective electrodes.
• That is, positively charged cations move toward the cathode and negatively charged anions move towards the anode.
• When the anions reach the anode, they are discharged through electron removal(oxidation), liberating neutral atoms or molecules at the electrode.
• When cations reach the cathode, they are neutralized through electron addition(reduction).

Electrolysis in a dilute solution of ${\mathrm{CuCl}}_2$ with Platinum electrodes:

• In an aqueous solution, dilute Silver nitrate dissociates to form Cupric ions (${\mathrm{Cu}}^{2+}$) and the Chloride ions (${\mathrm{Cl}}^{-}$) and the autoionization of water gives protons$\left({\mathrm{H}}^{+}\right)$ and Hydroxide ions$\left({\mathrm{OH}}^{-}\right)$.

$\underset{\mathrm{Cupric}\mathrm{chloride}}{{\mathrm{CuCl}}_2\left(\mathrm{aq}\right)}\to \underset{\mathrm{Cupric}\mathrm{ion}}{{\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)}+\underset{\mathrm{Chloride}\mathrm{ion}}{2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)}$

$\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\mathrm{Protons}}{{\mathrm{H}}^{+}\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydroxide}\mathrm{ions}}{{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)}$

• Thus, the dilute aqueous Cupric chloride solution contains protons, Hydroxide ions, Cupric ions, and Chloride ions.
• However, the anode(positive electrode) attracts Hydroxide ions and Chloride ions.
• Chloride ions have a higher reduction potential than Oxygen.
• Thus, the Chloride ions will be deposited at the cathode.
  $\underset{\mathrm{Chloride}\mathrm{ions}}{2{\mathrm{Cl}}^{-}}\to \underset{\mathrm{Chlorine}}{{\mathrm{Cl}}_2}+\underset{\mathrm{Electron}}{2{\mathrm{e}}^{-}}$
• The cathode is a negative electrode and it attracts protons and Cupric ions.
• Cupric ions have a higher reduction potential than the water molecule
• Thus, the Cupric ions will be deposited at the cathode.
• Cupric ions accept two electrons to form $\mathrm{Cu}$ metal and get deposited on the cathode.

$\underset{\mathrm{Cupric}\mathrm{ions}}{{\mathrm{Cu}}^{2+}}+\underset{\mathrm{Electron}}{2{\mathrm{e}}^{-}}\to \underset{\mathrm{Copper}}{\mathrm{Cu}}$

• The net cell reaction is $\underset{\mathrm{Chloride}\mathrm{ions}}{2{\mathrm{Cl}}^{-}}+\underset{\mathrm{Cupric}\mathrm{ions}}{{\mathrm{Cu}}^{2+}}\to \underset{\mathrm{Chlorine}}{{\mathrm{Cl}}_2}+\underset{\mathrm{Copper}}{\mathrm{Cu}}$

Therefore, in the electrolysis of dilute aqueous Copper chloride, using Platinum electrodes,

$\mathrm{Cu}$ will deposit at the cathode and dissolve at the anode to form ${\mathrm{Cu}}^{2+}$ ions.