Discussion
Which of the following statements best describes the flow of electrons in the above electrochemical cell ?
Answer: D
Electrons flow from the Zn electrode to the Pb electrode through the Cu wire.
The standard reduction potentials are Zn2+/Zn -0.76 V and Pb2+/Pb -0.13 V. Zinc, with the more negative potential, is oxidised and is the anode; lead ions are reduced at the cathode. The cell reaction is Zn + Pb2+ → Zn2+ + Pb, with E°cell = 0.63 V.
Electrons released at the zinc anode travel through the external circuit, the Cu wire, to the lead cathode. Electrons never pass through the salt bridge; it carries ions that keep the two solutions electrically neutral. That rules out both salt-bridge options, and the option with electrons going from Pb to Zn has the direction reversed.
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