Question

Complete the following ionic equations in reference to electrolysis and electroplating

$$\begin{gathered} 1.\mathrm{Na}\left[\mathrm{Ag}{\left(\mathrm{CN}\right)}_2\right]\rightleftharpoons \mathrm{\_\_\_\_\_}+\mathrm{\_\_\_\_\_\_} \\ 2.{\mathrm{H}}_2\mathrm{O}\rightleftharpoons \mathrm{\_\_\_\_\_\_}+\mathrm{\_\_\_\_\_\_\_} \\ 3.{\mathrm{Ag}}^{+}+\mathrm{\_\_\_\_}\to \mathrm{\_\_\_\_\_} \\ 4.\mathrm{Ag}-\mathrm{\_\_\_\_}\to \mathrm{\_\_\_\_\_\_} \end{gathered}$$

Answer 1

Electroplating with silver

1. Dissociation of $\mathrm{Na}\left[\mathrm{Ag}{\left(\mathrm{CN}\right)}_2\right]$

• Cathode - The article to be plated
• Anode - Pure plate or block of silver
• Sodium silver cyanide solution dissociates into sodium ions and silver cyanide ions, which further dissociate into silver ions and cyanide ions

$$\begin{gathered} \mathrm{Na}\left[\mathrm{Ag}{\left(\mathrm{CN}\right)}_2\right]\rightleftharpoons {\mathbf{Na}}^{\mathbf{+}}+\mathbf{}\mathbf{\left[}\mathbf{Ag}{\mathbf{\left(}\mathbf{CN}\mathbf{\right)}}_{\mathbf{2}}{\mathbf{]}}^{-} \\ \right[\mathrm{Ag}{\left(\mathrm{CN}\right)}_2{]}^{-}\rightleftharpoons {\mathrm{Ag}}^{+}+2{\mathrm{CN}}^{-} \end{gathered}$$

2. Dissociation of ${\mathrm{H}}_2\mathrm{O}$

• The water is dissociated into hydrogen ions as positive ions and hydroxyl ions as negative ions

${\mathrm{H}}_2\mathrm{O}\rightleftharpoons {\mathbf{H}}^{\mathbf{+}}\mathbf{}+\mathbf{}{\mathbf{OH}}^{\mathbf{-}}$

3. Electrode reaction

• The reduction half-reaction occurring at the cathode is given in this reaction
• The positively charged ${\mathrm{Ag}}^{+}$ions are discharged at the cathode by accepting electrons and deposited as a thin film of metallic silver on the cathode(article)

${\mathrm{Ag}}^{+}+\mathbf{}{\mathbf{e}}^{\mathbf{-}}\to \mathbf{}\mathbf{Ag}$

4. Electrode reaction

• The oxidation half-reaction occurring at the anode is given in this reaction
• The silver atoms from the anode lose electrons and enter into the solution as silver ions

$\mathrm{Ag}-\mathbf{}{\mathbf{e}}^{\mathbf{-}}\to {\mathbf{Ag}}^{\mathbf{+}}$