A student assembles a galvanic cell at 25∘C using a strip of zinc metal immersed in 1.0MZnSO4 solution (colorless) and a strip of copper metal immersed in 1.0MCuSO4 solution (deep blue). The two half-cells are connected by a salt bridge containing saturated KNO3(aq), and the external circuit is completed with a wire and voltmeter.
After the cell has been allowed to deliver current for 10 minutes, the student records the following observations.
• The zinc strip has become noticeably thinner and is coated with a dark, dull layer.
• The blue color of the copper solution near the copper electrode becomes noticeably lighter.
• White crystals appear at the end of the salt bridge dipping into the copper half-cell; no visible change is seen at the other end.
• The voltmeter reads +1.10 V when its positive terminal is attached to the copper electrode.
Answer the following questions about the operation of the cell.
(a) Identify which electrode is the anode. Justify your answer with reference to TWO of the recorded observations.
(b) Explain, at the particulate level, why the blue color of the CuSO4 solution fades in the vicinity of the copper electrode as the cell operates.
(c) Write the oxidation and reduction half-reactions occurring in the cell, including phase symbols.
(d) Predict the direction in which the NO3− ions migrate through the salt bridge. Justify your answer in terms of charge balance inside the half-cells.