---
title: "A student tests an electrochemical cell designed to recover copper from a waste solution. One half-cell contains a (\\text{Zn(s)}\\) electrode in (1.0 \\text{ M}\\) (\\text{Zn}^{2+}\\text{(aq)})\\), and the other contains a (\\text{Cu(s)}\\) electrode in (1.0 \\text{ M}\\) (\\text{Cu}^{2+}\\text{(aq)})\\). The half-cells are connected by a (\\text{KNO}_3\\) salt bridge, and no external power source is used. The student proposes that the following half-reaction occurs spontaneously at the zinc electrode.  [\\text{Zn(s)} \\rightarrow \\text{Zn}^{2+}\\text{(aq)}+2e^-\\]  Which observation would provide the most direct experimental evidence that the proposed oxidation half-reaction occurs spontaneously at the zinc electrode?"
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url: "https://nerd-notes.com/ubq/119504/"
date_modified: "2026-08-19T12:40:51+00:00"
---

# A student tests an electrochemical cell designed to recover copper from a waste solution. One half-cell contains a (\text{Zn(s)}\) electrode in (1.0 \text{ M}\) (\text{Zn}^{2+}\text{(aq)})\), and the other contains a (\text{Cu(s)}\) electrode in (1.0 \text{ M}\) (\text{Cu}^{2+}\text{(aq)})\). The half-cells are connected by a (\text{KNO}_3\) salt bridge, and no external power source is used. The student proposes that the following half-reaction occurs spontaneously at the zinc electrode.

[\text{Zn(s)} \rightarrow \text{Zn}^{2+}\text{(aq)}+2e^-\]

Which observation would provide the most direct experimental evidence that the proposed oxidation half-reaction occurs spontaneously at the zinc electrode?

A student tests an electrochemical cell designed to recover copper from a waste solution. One half-cell contains a (\text{Zn(s)}\) electrode in (1.0 \text{ M}\) (\text{Zn}^{2+}\text{(aq)})\), and the other contains a (\text{Cu(s)}\) electrode in (1.0 \text{ M}\) (\text{Cu}^{2+}\text{(aq)})\). The half-cells are connected by a (\text{KNO}_3\) salt bridge, and no external power source is used. The student proposes that the following half-reaction occurs spontaneously at the zinc electrode.

[\text{Zn(s)} \rightarrow \text{Zn}^{2+}\text{(aq)}+2e^-\]

Which observation would provide the most direct experimental evidence that the proposed oxidation half-reaction occurs spontaneously at the zinc electrode?

- **A.** With the circuit open, the voltmeter reads (+1.10 \text{ V}\) when its positive lead is connected to the (\text{Cu(s)}\) electrode.
- **B.** After the circuit is closed, the (\text{Cu(s)}\) electrode gains mass while ([\text{Cu}^{2+}]\) decreases and electrons enter that electrode through the wire.
- **C.** After the circuit is closed, (\text{NO}_3^-\text{(aq)})\) ions migrate toward the zinc half-cell while electrical current passes through the external circuit.
- **D.** After the circuit is closed with no external power source, the (\text{Zn(s)}\) electrode loses mass, ([\text{Zn}^{2+}]\) increases, and electrons flow away from that electrode.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119504/*