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title: "A student constructs two separate concentration cells at \\(298\\text{ K}\\). Cell 1 consists of two \\(\\text{Ag(s)}\\) electrodes immersed in separate beakers containing \\(\\text{AgNO}_3(aq)\\). Cell 2 consists of two \\(\\text{Cu(s)}\\) electrodes immersed in separate beakers containing \\(\\text{CuSO}_4(aq)\\). In both setups, the half-cells are connected by a salt bridge and an external wire, and the reaction quotient is defined as \\(Q = \\dfrac{[\\text{cation}]_{\\text{anode}}}{[\\text{cation}]_{\\text{cathode}}}\\). The graph shows the measured cell potential, \\(E_{\\text{cell}}\\), as a function of \\(\\log Q\\) as each cell discharges toward equilibrium.  Which of the following correctly identifies the curve corresponding to Cell 1 (\\(\\text{Ag/Ag}^+\\)) and provides the correct explanation for why both curves intersect the horizontal axis at \\(\\log Q = 0\\)?"
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date_modified: "2026-08-23T04:23:42+00:00"
---

# A student constructs two separate concentration cells at \(298\text{ K}\). Cell 1 consists of two \(\text{Ag(s)}\) electrodes immersed in separate beakers containing \(\text{AgNO}_3(aq)\). Cell 2 consists of two \(\text{Cu(s)}\) electrodes immersed in separate beakers containing \(\text{CuSO}_4(aq)\). In both setups, the half-cells are connected by a salt bridge and an external wire, and the reaction quotient is defined as \(Q = \dfrac{[\text{cation}]_{\text{anode}}}{[\text{cation}]_{\text{cathode}}}\). The graph shows the measured cell potential, \(E_{\text{cell}}\), as a function of \(\log Q\) as each cell discharges toward equilibrium.

Which of the following correctly identifies the curve corresponding to Cell 1 (\(\text{Ag/Ag}^+\)) and provides the correct explanation for why both curves intersect the horizontal axis at \(\log Q = 0\)?

A student constructs two separate concentration cells at \(298\text{ K}\). Cell 1 consists of two \(\text{Ag(s)}\) electrodes immersed in separate beakers containing \(\text{AgNO}_3(aq)\). Cell 2 consists of two \(\text{Cu(s)}\) electrodes immersed in separate beakers containing \(\text{CuSO}_4(aq)\). In both setups, the half-cells are connected by a salt bridge and an external wire, and the reaction quotient is defined as \(Q = \dfrac{[\text{cation}]_{\text{anode}}}{[\text{cation}]_{\text{cathode}}}\). The graph shows the measured cell potential, \(E_{\text{cell}}\), as a function of \(\log Q\) as each cell discharges toward equilibrium.

Which of the following correctly identifies the curve corresponding to Cell 1 (\(\text{Ag/Ag}^+\)) and provides the correct explanation for why both curves intersect the horizontal axis at \(\log Q = 0\)?

![A Cartesian graph with a horizontal axis labeled \(\log Q\) and a vertical axis labeled \(E_{\text{cell}}\text{ (V)}\). The horizontal axis has tick marks labeled from \(-4.0\) to \(0.0\) in increments of \(1.0\). The vertical axis has tick marks labeled from \(0.00\) to \(0.24\) in increments of \(0.06\). Two straight lines originate at negative values of \(\log Q\) and terminate at the origin \((0.0, 0.00)\). A solid line, labeled Curve 1, passes through the coordinates \((-4.0, 0.24)\), \((-3.0, 0.18)\), \((-2.0, 0.12)\), \((-1.0, 0.06)\), and \((0.0, 0.00)\). A dashed line, labeled Curve 2, passes through the coordinates \((-4.0, 0.12)\), \((-2.0, 0.06)\), and \((0.0, 0.00)\). A legend in the upper right displays: solid line = Curve 1; dashed line = Curve 2. No other particles, labels, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787459021-MFXDXM.jpg)

- **A.** Curve 1 (solid line), because \(n = 1\) for the \(\text{Ag}^+(aq)/\text{Ag(s)}\) half-reaction gives a steeper slope of magnitude \(\dfrac{0.0592\text{ V}}{n}\); both curves intersect at \(\log Q = 0\) because at equilibrium the ion concentrations in both half-cells are equal (\(Q = K = 1\)), resulting in \(E_{\text{cell}} = 0.00\text{ V}\).
- **B.** Curve 2 (dashed line), because transferring only \(1\text{ mol } e^-\text{/mol}_{\text{rxn}}\) produces a smaller change in potential per unit of \(\log Q\); both curves intersect at \(\log Q = 0\) because at equilibrium the ion concentrations in both half-cells are equal (\(Q = K = 1\)), resulting in \(E_{\text{cell}} = 0.00\text{ V}\).
- **C.** Curve 1 (solid line), because \(n = 1\) for the \(\text{Ag}^+(aq)/\text{Ag(s)}\) half-reaction gives a steeper slope of magnitude \(\dfrac{0.0592\text{ V}}{n}\); both curves intersect at \(\log Q = 0\) because the cathode compartment has completely depleted its concentration of metal cations to \(0\text{ M}\).
- **D.** Curve 2 (dashed line), because the greater molar mass of \(\text{Ag}\) relative to \(\text{Cu}\) reduces the rate at which cell potential changes; both curves intersect at \(\log Q = 0\) because standard cell potential \(E^\circ_{\text{cell}}\) is defined only when \(\log Q \le 0\).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120367/*