Electrochemical Cell
A galvanic cell is an electrochemical cell that converts chemical energy of a spontaneous redox reaction into electrical energy. It consists of two half cells, the half cell in which oxidation takes place is called as anode and the other half cell where reduction takes place is called as cathode. Anode has negative potential with respect to the solution whereas cathode has positive potential with respect to the solution. As soon as the switch is in the on position, the electrons flow from the negative electrode to positive electrode and the direction of current flow is opposite to that of electron flow. The potential difference between two electrodes is called cell potential and is measured in volts. When no current is drawn from the cell, then cell potential is termed as cell electromotive force. The cell potential is given by Nernst equation.
Which of the given statements is true about the given cell reaction?
Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2 Ag(s)
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → The Cu2+/Cu half cell acts as an anode.
In a galvanic cell, oxidation takes place at the anode and reduction at the cathode. Splitting the cell reaction into its two half reactions shows which is which:
\( \displaystyle \text{Anode (oxidation): }\ce{Cu(s) -> Cu^2+(aq) + 2e^-} \)
\( \displaystyle \text{Cathode (reduction): }\ce{2Ag^+(aq) + 2e^- -> 2Ag(s)} \)
Copper loses electrons, so the Cu2+/Cu half cell is the anode; silver ions gain electrons, so the \( \ce{Ag^{+}} \)/Ag half cell is the cathode. The cell is written as:
\( \displaystyle \ce{Cu(s)}|\ce{Cu^2+(aq)}||\ce{Ag^+(aq)}|\ce{Ag(s)} \)
The reaction is feasible because the cell potential is positive:
\( \displaystyle E^\circ_{\mathrm{cell}}=E^\circ_{\mathrm{cathode}}-E^\circ_{\mathrm{anode}}=0.80-0.34=+0.46\ \mathrm{V} \)
So the true statement is that the Cu2+/Cu half cell acts as an anode.
Why the other options are incorrect
Option (1) The Ag+/Ag half cell acts as an anode — Incorrect. \( \ce{Ag^{+}} \) is reduced to Ag, so this half cell is the cathode.
Option (3) Above cell reaction is not possible — Incorrect. E°cell = +0.46 V is positive, so ΔG° is negative and the reaction is spontaneous.
Option (4) It is one electron change cell reaction — Incorrect. One Cu atom gives two electrons, taken up by two \( \ce{Ag^{+}} \) ions, so n = 2.
NCERT (2026-27 edition):
Galvanic Cells – “… Under this convention the emf of the cell is positive and is given by the potential of the half-cell on the right hand side minus the potential of the half-cell on the left hand side i.e., Ecell = Eright – Eleft. This is illustrated by the following example:
Cell reaction: Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2Ag(s)
Half-cell reactions: Cathode (reduction): 2Ag+(aq) + 2e– → 2Ag(s)
Anode (oxidation): Cu(s) → Cu2+(aq) + 2e–
… silver electrode acts as a cathode and copper electrode acts as an anode.”