230-- Which figure shows the standard electrode for a copper half-cell? (Temperature is constant and equal to $25^\circ$C.) [Figure: Four diagrams of electrochemical half-cells labeled (1), (2), (3), (4). Options (1) and (3) show copper plates with $\mathrm{Cu^{2+}}$ $(1\,\mathrm{mol.L^{-1}})$ solution; option (2) shows a platinum plate with $\mathrm{Cu^{2+}}$ $(1\,\mathrm{mol.L^{-1}})$; option (4) shows a copper plate with $\mathrm{H^+}$ $(1\,\mathrm{mol.L^{-1}})$ and distilled water.]
\textbf{230--} Which figure shows the standard electrode for a copper half-cell? (Temperature is constant and equal to $25^\circ$C.)
\textit{[Figure: Four diagrams of electrochemical half-cells labeled (1), (2), (3), (4). Options (1) and (3) show copper plates with $\mathrm{Cu^{2+}}$ $(1\,\mathrm{mol.L^{-1}})$ solution; option (2) shows a platinum plate with $\mathrm{Cu^{2+}}$ $(1\,\mathrm{mol.L^{-1}})$; option (4) shows a copper plate with $\mathrm{H^+}$ $(1\,\mathrm{mol.L^{-1}})$ and distilled water.]}
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