AP Chemistry Unit 9: Thermodynamics and Electrochemistry Practice Exam

Assessment for Unit 9: Thermodynamics and Electrochemistry

Estimated Time: 60 minutes

Exam Details

Questions: 28 total (28 multiple choice)
Time: 60 minutes (recommended)
Topics Covered: Unit 9: Thermodynamics and Electrochemistry
Format: Multiple Choice questions matching real exam difficulty
Scoring: Instant results with detailed explanations

A. Multiple-Choice Questions (28 Questions)

Select the one best answer for each question.

1. [Skill: 4.A | Topic: 9.1] A student considers four separate processes carried out under the stated conditions. Process 1: 1.0 mol of $H_2O(l)$ freezes to form 1.0 mol of $H_2O(s)$ at 0°C. Process 2: 1.0 mol of $CO_2(g)$ is compressed isothermally from 2.0 L to 1.0 L. Process 3: 1.0 mol of $NaCl(s)$ dissolves in 1.0 L of water at 25°C to form aqueous ions. Process 4: 1.0 mol of $H_2O(l)$ vaporizes to form 1.0 mol of $H_2O(g)$ at 25°C. Which process is expected to have the greatest positive change in the entropy of the system, $\Delta S_{sys}$?

(A)Process 1(B)Process 2(C)Process 3(D)Process 4

2. [Skill: 2.A | Topic: 9.1] A researcher compares the sign of $\Delta S_{sys}$ for the following balanced reactions carried out under the same conditions. Reaction I: $2H_2(g) + O_2(g) \rightarrow 2H_2O(g)$ Reaction II: $CaCO_3(s) \rightarrow CaO(s) + CO_2(g)$ Reaction III: $N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)$ Reaction IV: $2SO_2(g) + O_2(g) \rightarrow 2SO_3(g)$ Which reaction is expected to have $\Delta S_{sys} > 0$?

(A)Reaction I only(B)Reaction II only(C)Reaction III only(D)Reaction IV only

Refer to the figure below.

3. [Skill: 3.B | Topic: 9.1] A sample of an ideal gas is heated from $T_1$ to $T_2$ ($T_2 > T_1$) in a rigid, sealed container (constant volume). A student sketches Maxwell–Boltzmann distributions of molecular kinetic energy at the two temperatures. Which statement best describes the change in the entropy of the gas and the reason for that change?

(A)$\Delta S_{sys} < 0$ because increasing temperature forces the kinetic energies to become more uniform (less spread out).(B)$\Delta S_{sys} < 0$ because heating at constant volume reduces the number of possible microstates available to the gas.(C)$\Delta S_{sys} > 0$ because increasing temperature broadens the distribution of kinetic energies, increasing energy dispersal among accessible microstates.(D)$\Delta S_{sys} > 0$ because heating at constant volume decreases the average kinetic energy, allowing molecules to occupy more positions in the container.

Refer to the figure below.

4. [Skill: 5A | Topic: 9.10] A student investigates how the cell potential of a galvanic cell changes with concentration. The overall reaction is $Zn(s) + Cu^{2+}(aq) \rightarrow Zn^{2+}(aq) + Cu(s)$ At 25 °C, the student calculates $E_{cell}$ for several trials with different values of $Q = \dfrac{[Zn^{2+}]}{[Cu^{2+}]}$ and plots $E_{cell}$ versus $\log Q$. [Image Cue]: Graph, "Cell Potential vs log Q for a Zn/Cu Cell", x-axis: $\log Q$ (from −2 to +2), y-axis: $E_{cell}$ (V) (from 1.00 to 1.20). The plotted points form a straight line with negative slope passing through approximately (0, 1.10 V), (1, 1.07 V), (2, 1.04 V), (−1, 1.13 V), (−2, 1.16 V). Which of the following changes would move the cell to a new condition with a larger measured $E_{cell}$?

(A)Increase $[Zn^{2+}]$ while keeping $[Cu^{2+}]$ constant(B)Decrease $[Cu^{2+}]$ while keeping $[Zn^{2+}]$ constant(C)Decrease $[Zn^{2+}]$ while keeping $[Cu^{2+}]$ constant(D)Increase both $[Zn^{2+}]$ and $[Cu^{2+}]$ by the same factor

5. [Skill: 2B | Topic: 9.10] A galvanic cell is constructed as follows: $Zn(s) | Zn^{2+}(aq) || Cu^{2+}(aq) | Cu(s)$ The overall reaction is $Zn(s) + Cu^{2+}(aq) \rightarrow Zn^{2+}(aq) + Cu(s)$ At 25 °C, $E^\circ_{cell} = 1.10\text{ V}$. A student prepares the cell with $[Zn^{2+}] = 1.0\text{ M}$ and $[Cu^{2+}] = 0.10\text{ M}$. Which value is closest to $E_{cell}$ under these conditions? (Use $E = E^\circ - \dfrac{0.0592}{n}\log Q$ at 25 °C.)

(A)1.13 V(B)1.10 V(C)1.07 V(D)1.04 V

6. [Skill: 6A | Topic: 9.10] A student uses a fresh galvanic cell as a battery to power a small device. Over time, the measured cell potential decreases steadily and eventually reaches 0 V, even though both electrodes are still present. Which explanation best accounts for why the voltage drops to 0 V as the battery is used?

(A)Electrons are gradually consumed, so fewer electrons are available to flow through the circuit.(B)As reactants are converted to products, the reaction quotient $Q$ changes so that the cell reaction approaches equilibrium, reducing the driving force until $E_{cell} = 0$ at equilibrium.(C)The salt bridge stops working once any product forms, preventing charge balance and forcing the voltage to become 0 V.(D)The standard cell potential $E^\circ_{cell}$ decreases during operation because the identity of the half-reactions changes as the battery runs.

7. [Skill: 5.B | Topic: 9.2] A student is given the standard molar entropies, $S^\circ$, shown in the table. | Species | $S^\circ$ (J mol$^{-1}$ K$^{-1}$) | |---|---:| | $N_2(g)$ | 191.5 | | $H_2(g)$ | 130.6 | | $NH_3(g)$ | 192.8 | Using the data, what is the value of $\Delta S^\circ_{\rm rxn}$ for the reaction below at 298 K? $N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)$

(A)+198 J mol$^{-1}$ K$^{-1}$(B)+66.0 J mol$^{-1}$ K$^{-1}$(C)−66.0 J mol$^{-1}$ K$^{-1}$(D)−198 J mol$^{-1}$ K$^{-1}$

8. [Skill: 5.B | Topic: 9.2] A reference table provides the following standard molar entropies, $S^\circ$, at 298 K. | Species | $S^\circ$ (J mol$^{-1}$ K$^{-1}$) | |---|---:| | $H_2(g)$ | 130.6 | | $O_2(g)$ | 205.0 | | $H_2O(l)$ | 69.9 | | $H_2O(g)$ | 188.8 | Which of the following processes has the greatest (most positive) standard entropy change, $\Delta S^\circ$?

(A)$H_2O(l) \rightarrow H_2O(g)$(B)$2H_2(g) + O_2(g) \rightarrow 2H_2O(g)$(C)$2H_2(g) + O_2(g) \rightarrow 2H_2O(l)$(D)$2H_2O(g) \rightarrow 2H_2O(l)$

9. [Skill: 5.B | Topic: 9.2] A student investigates the thermal decomposition of calcium carbonate and consults a table of standard molar entropies. Reaction: $CaCO_3(s) \rightarrow CaO(s) + CO_2(g)$ | Species | $S^\circ$ (J mol$^{-1}$ K$^{-1}$) | |---|---:| | $CaCO_3(s)$ | 92.9 | | $CaO(s)$ | 39.8 | | $CO_2(g)$ | 213.7 | What is the value of $\Delta S^\circ_{\rm rxn}$ for the reaction at 298 K?

(A)−267 J mol$^{-1}$ K$^{-1}$(B)−160.6 J mol$^{-1}$ K$^{-1}$(C)+160.6 J mol$^{-1}$ K$^{-1}$(D)+267 J mol$^{-1}$ K$^{-1}$

10. 1. [Skill: 5.A | Topic: 9.3] A student is evaluating the thermodynamic favorability of the combustion of ethanol under standard conditions. Reaction: $C_2H_5OH(l) + 3O_2(g) \rightarrow 2CO_2(g) + 3H_2O(l)$ Standard Gibbs free energies of formation, $\Delta G_f^\circ$ (kJ/mol): - $CO_2(g)$: −394.4 - $H_2O(l)$: −237.1 - $C_2H_5OH(l)$: −174.8 - $O_2(g)$: 0 Which of the following best describes the value of $\Delta G^\circ_{rxn}$ and whether the reaction is thermodynamically favored under standard conditions?

(A)$\Delta G^\circ_{rxn} \approx -1325\ \text{kJ/mol}$, so the reaction is thermodynamically favored(B)$\Delta G^\circ_{rxn} \approx +1325\ \text{kJ/mol}$, so the reaction is thermodynamically favored(C)$\Delta G^\circ_{rxn} \approx -1325\ \text{kJ/mol}$, so the reaction is not thermodynamically favored(D)$\Delta G^\circ_{rxn} \approx +1325\ \text{kJ/mol}$, so the reaction is not thermodynamically favored

11. 2. [Skill: 5.A | Topic: 9.3] A student studies a process with measured thermodynamic quantities under standard conditions: Process: $X(s) \rightarrow Y(aq)$ At standard conditions, $\Delta H^\circ = +25.7\ \text{kJ/mol}$ and $\Delta S^\circ = +108\ \text{J/(mol\cdot K)}$. At which temperature range is the process thermodynamically favored under standard conditions?

(A)The process is thermodynamically favored at all temperatures(B)The process is thermodynamically favored only at temperatures below 238 K(C)The process is thermodynamically favored only at temperatures above 238 K(D)The process is never thermodynamically favored

12. 3. [Skill: 6.A | Topic: 9.3] A teacher provides information about four different processes under standard conditions. Process information (signs only): - Process 1: $\Delta H^\circ < 0$, $\Delta S^\circ > 0$ - Process 2: $\Delta H^\circ < 0$, $\Delta S^\circ < 0$ - Process 3: $\Delta H^\circ > 0$, $\Delta S^\circ > 0$ - Process 4: $\Delta H^\circ > 0$, $\Delta S^\circ < 0$ Based on $\Delta G^\circ = \Delta H^\circ - T\Delta S^\circ$, which process is thermodynamically favored under standard conditions at all temperatures?

(A)Process 1 only(B)Process 2 only(C)Process 3 only(D)Process 4 only

13. [Skill: 7.A | Topic: 9.4] A sample of diamond is stored at 298 K and 1 atm for many years. Under these conditions, the conversion of diamond to graphite is thermodynamically favored (the process has a negative Gibbs free energy change, ΔG < 0). Which of the following best explains why little or no graphite is observed over this time period?

(A)The diamond-to-graphite conversion has a large activation energy, so the reaction rate is extremely slow at 298 K.(B)Because ΔG < 0, the reaction should proceed quickly until equilibrium is reached.(C)The system must already be at equilibrium because diamond does not convert to graphite.(D)The reaction is thermodynamically favored only at high temperatures, so it cannot occur at 298 K.

Refer to the figure below.

14. [Skill: 4.A | Topic: 9.4] Two different reaction pathways are proposed for the same overall reaction, and the reaction is known to be thermodynamically favored under the conditions studied (ΔG < 0). [Image Cue]: Reaction coordinate diagram, "Two Pathways for a Thermodynamically Favored Reaction"; x-axis: Reaction Progress, y-axis: Potential Energy. Both pathways start at the same reactant energy and end at the same lower product energy (exergonic). Pathway 1 has a much higher peak (larger activation energy) than Pathway 2. Which pathway corresponds to a process more likely to be under kinetic control at the temperature studied, and why?

(A)Pathway 1, because the larger activation energy leads to a slower rate even though products are lower in energy.(B)Pathway 1, because a larger activation energy makes ΔG more negative and therefore less likely to occur.(C)Pathway 2, because the smaller activation energy increases the likelihood that the reaction is thermodynamically favored.(D)Pathway 2, because the smaller activation energy means the system must already be at equilibrium.

15. [Skill: 5.A | Topic: 9.4] A sealed rigid container is filled with $H_2(g)$ and $O_2(g)$ at 298 K. Thermodynamic data indicate that forming liquid water from these gases is strongly favored under these conditions. Overall reaction: $2H_2(g) + O_2(g) \rightarrow 2H_2O(l)$ The mixture is monitored for several hours at 298 K, and no measurable change in pressure is observed. Which statement best describes the system during the monitoring period?

(A)The system is under kinetic control because the activation energy is high; the lack of reaction does not imply the system is at equilibrium.(B)The system is at equilibrium because macroscopic properties (pressure) do not change with time.(C)The reaction is not thermodynamically favored at 298 K, which explains why it does not occur.(D)Because the forward reaction does not occur, the reverse reaction rate must be greater than the forward reaction rate.

16. **1.** [Skill: 2A | Topic: 9.5] A student studies the equilibrium shown below at $298\ \text{K}$. $A(g) \rightleftharpoons B(g)$ The equilibrium constant for the reaction is reported as $K = 4.5\times 10^3$ at $298\ \text{K}$. Which of the following best describes $\Delta G^\circ$ for the reaction at $298\ \text{K}$ and what is favored at equilibrium under standard conditions? (Use $R = 8.314\ \text{J mol}^{-1}\text{K}^{-1}$.)

(A)$\Delta G^\circ \approx -2.1\times 10^4\ \text{J mol}^{-1}$; products are favored ($K>1$)(B)$\Delta G^\circ \approx +2.1\times 10^4\ \text{J mol}^{-1}$; products are favored ($K>1$)(C)$\Delta G^\circ \approx -2.1\times 10^4\ \text{J mol}^{-1}$; reactants are favored ($K<1$)(D)$\Delta G^\circ \approx +2.1\times 10^4\ \text{J mol}^{-1}$; reactants are favored ($K<1$)

17. **2.** [Skill: 3A | Topic: 9.5] Three different reactions are studied at $298\ \text{K}$ under standard conditions. The standard free energy changes are shown. - Reaction I: $\Delta G^\circ = -1.0\ \text{kJ mol}^{-1}$ - Reaction II: $\Delta G^\circ = +20.\ \text{kJ mol}^{-1}$ - Reaction III: $\Delta G^\circ = 0\ \text{kJ mol}^{-1}$ Which statement about the equilibrium constants at $298\ \text{K}$ is correct? (Use the relationship between $K$ and $\Delta G^\circ$ qualitatively and/or $\Delta G^\circ=-RT\ln K$.)

(A)Reaction I has $K$ slightly greater than 1; Reaction II has $K$ much less than 1; Reaction III has $K=1$(B)Reaction I has $K$ slightly less than 1; Reaction II has $K$ much greater than 1; Reaction III has $K=1$(C)Reaction I has $K$ close to 0; Reaction II has $K$ close to 1; Reaction III has $K$ much greater than 1(D)All three reactions have $K$ close to 1 because the values of $\Delta G^\circ$ are all within about $\pm 20\ \text{kJ mol}^{-1}$

18. **3.** [Skill: 2A | Topic: 9.5] For the reaction $C(g) \rightleftharpoons D(g)$, a student is told that $\Delta G^\circ = +5.0\ \text{kJ mol}^{-1}$ at $298\ \text{K}$. For the purposes of this question, assume $\Delta G^\circ$ remains approximately constant between $298\ \text{K}$ and $596\ \text{K}$. Which option correctly compares the equilibrium constant $K$ at $298\ \text{K}$ to the equilibrium constant at $596\ \text{K}$? (Use $K=e^{-\Delta G^\circ/RT}$ and $R=8.314\ \text{J mol}^{-1}\text{K}^{-1}$.)

(A)$K_{298}\approx 0.13$ and $K_{596}\approx 0.36$; increasing $T$ increases $K$ but $K$ remains less than 1(B)$K_{298}\approx 0.13$ and $K_{596}\approx 2.7$; increasing $T$ makes $K$ greater than 1(C)$K_{298}\approx 7.5$ and $K_{596}\approx 2.7$; increasing $T$ decreases $K$ but both are greater than 1(D)$K_{298}\approx 7.5$ and $K_{596}\approx 0.36$; increasing $T$ changes $K$ from greater than 1 to less than 1

19. 1. [Skill: 2A | Topic: 9.6] A student compares the dissolution of two ionic solids in water at 298 K. | Salt | $\Delta $H^$\circ_{\text{soln}}$ (kJ/mol) | $\Delta $S^$\circ_{\text{soln}}$ (J/mol·K) | |---|---:|---:| | Salt X | +18 | +95 | | Salt Y | −18 | −95 | Based on the data, which statement best predicts how the solubility of each salt will change when the temperature is increased above 298 K?

(A)The solubility of Salt X increases with temperature, and the solubility of Salt Y decreases with temperature.(B)The solubility of Salt X decreases with temperature, and the solubility of Salt Y increases with temperature.(C)The solubility of both salts increases with temperature because increasing temperature always favors dissolution.(D)The solubility of both salts decreases with temperature because dissolution disrupts the solid and is therefore less favorable at higher temperature.

Refer to the figure below.

20. 2. [Skill: 2A | Topic: 9.6] A student measures the solubility of an ionic compound, MZ, in water at several temperatures. [Image Cue]: Line graph, “Solubility of MZ in Water vs. Temperature”; x-axis = Temperature (°C) from 0 to 80; y-axis = Solubility (g solute / 100 g water) from 0 to 40; key trend: solubility decreases approximately linearly from 30 at 10°C to 12 at 70°C. Which conclusion about $\Delta $H^$\circ_{\text{soln}}$ for MZ(s) $\rightarrow $M^+(aq) + Z^-(aq) is most consistent with the data?

(A)The dissolution is endothermic because solubility decreases as temperature increases.(B)The dissolution is exothermic because solubility decreases as temperature increases.(C)The dissolution must have $\Delta $H^$\circ_{\text{soln}} $= 0 because solubility depends only on entropy.(D)The sign of $\Delta $H^$\circ_{\text{soln}}$ cannot be inferred from solubility trends because $\Delta $G^$\circ$ depends only on lattice energy.

21. 3. [Skill: 4A | Topic: 9.6] A student observes that 0.10$\ \text{mol}$ of an ionic solid AB(s) dissolves readily in 1.0$\ \text{L}$ of water at 298 K. A calorimetry experiment indicates that the dissolution process is endothermic ($\Delta $H^$\circ_{\text{soln}} $> 0). Which explanation best accounts for why AB can still be soluble at 298 K despite an endothermic enthalpy of dissolution?

(A)The entropy change for dissolution is sufficiently positive that the -T$\Delta $S^$\circ$ term outweighs $\Delta $H^$\circ$, making $\Delta $G^$\circ$ negative.(B)The entropy change for dissolution must be negative because water molecules become more ordered around ions, and negative $\Delta $S^$\circ$ makes $\Delta $G^$\circ$ negative.(C)Because $\Delta $H^$\circ_{\text{soln}} $> 0, $\Delta $G^$\circ$ must be positive at all temperatures, so the observation implies an experimental error.(D)Solubility is determined only by the strength of ion-dipole attractions, so $\Delta $S^$\circ$ is not relevant to predicting whether dissolution is thermodynamically favorable.

22. [Skill: 5A | Topic: 9.7] A student investigates the electrolysis of molten sodium chloride. The overall process is represented by the balanced equation: 2 NaCl(l) → 2 Na(l) + Cl_2(g) At 25°C, the standard Gibbs free energy change for the reaction is positive (ΔG° > 0). The student observes that when the electrolytic cell is connected to a DC power supply, sodium metal forms at one electrode and chlorine gas forms at the other. Which of the following best explains why the products form only when the power supply is connected?

(A)The applied electrical energy supplies work that drives a thermodynamically unfavorable process to occur.(B)Connecting the power supply lowers ΔG° for the reaction by increasing the temperature of the molten salt.(C)The power supply acts as a catalyst, decreasing the activation energy and making ΔG° negative.(D)The reaction is spontaneous under standard conditions, but proceeds too slowly without electricity.

23. [Skill: 2A | Topic: 9.7] In a biochemical system, the formation of glucose-6-phosphate from glucose is thermodynamically unfavorable when considered alone. Two reactions are proposed: Reaction 1: ATP(aq) + E(aq) → ADP(aq) + E–P(aq) ΔG° = −32 kJ/mol Reaction 2: E–P(aq) + glucose(aq) → glucose-6-phosphate(aq) + E(aq) ΔG° = +14 kJ/mol E is an enzyme and E–P is a phosphorylated enzyme intermediate. Which of the following best supports the claim that coupling these reactions can drive the formation of glucose-6-phosphate under standard conditions?

(A)Adding the ΔG° values shows the overall process has ΔG° = −18 kJ/mol, and the reactions share the intermediate E–P, so the coupled process is thermodynamically favorable.(B)Because Reaction 2 has ΔG° > 0, it cannot occur under any circumstances, even if coupled to another reaction.(C)The enzyme E makes Reaction 2 spontaneous by changing the value of ΔG° from positive to negative.(D)The overall ΔG° must be found by subtracting the ΔG° values, giving +46 kJ/mol, which shows coupling makes the process unfavorable.

Refer to the figure below.

24. [Skill: 4.A | Topic: 9.8] A student assembles a galvanic cell at 25°C with the following cell diagram: $\mathrm{Zn(s)\ |\ Zn^{2+}(aq,\ 1.0\ M)\ ||\ Cu^{2+}(aq,\ 1.0\ M)\ |\ Cu(s)}$ A salt bridge contains $\mathrm{KNO_3(aq)}$. After the cell operates for several minutes, the Zn electrode is observed to decrease in mass. Which of the following statements correctly describes the cell operation?

(A)Electrons flow through the external wire from the Cu electrode to the Zn electrode; $\mathrm{K^+}$ migrates through the salt bridge toward the Zn half-cell.(B)Electrons flow through the external wire from the Zn electrode to the Cu electrode; $\mathrm{NO_3^-}$ migrates through the salt bridge toward the Zn half-cell.(C)Electrons flow through the external wire from the Zn electrode to the Cu electrode; $\mathrm{K^+}$ migrates through the salt bridge toward the Zn half-cell.(D)Electrons flow through the external wire from the Cu electrode to the Zn electrode; $\mathrm{NO_3^-}$ migrates through the salt bridge toward the Cu half-cell.

25. [Skill: 2.A | Topic: 9.8] An electrolytic cell is set up for copper plating. The cell contains a beaker of $\mathrm{CuSO_4(aq)}$ with two electrodes: a copper metal strip and a clean metal spoon. The copper strip is connected to the positive terminal of an external power supply, and the spoon is connected to the negative terminal. After the power supply runs for several minutes, a layer of copper metal is observed on the spoon. Which of the following correctly identifies (i) the anode and cathode and (ii) which electrode gains mass?

(A)Anode = spoon, cathode = copper strip; the copper strip gains mass.(B)Anode = spoon, cathode = copper strip; the spoon gains mass.(C)Anode = copper strip, cathode = spoon; the spoon gains mass.(D)Anode = copper strip, cathode = spoon; the copper strip gains mass.

26. **1. [Skill: 4A | Topic: 9.9]** A student constructs a voltaic cell using the half-cells $Zn(s) \mid Zn^{2+}(aq)$ and $Ag^+(aq) \mid Ag(s)$ under standard conditions. A table of standard reduction potentials is provided. - $Ag^+(aq) + e^- \rightarrow Ag(s)$, $E^\circ = +0.80\ \text{V}$ - $Zn^{2+}(aq) + 2e^- \rightarrow Zn(s)$, $E^\circ = -0.76\ \text{V}$ Which of the following statements about the overall cell reaction under standard conditions is correct?

(A)The cell has $E^\circ_{cell} = +1.56\ \text{V}$ and $\Delta G^\circ < 0$, so the reaction is thermodynamically favored.(B)The cell has $E^\circ_{cell} = +0.04\ \text{V}$ and $\Delta G^\circ < 0$, so the reaction is thermodynamically favored.(C)The cell has $E^\circ_{cell} = -1.56\ \text{V}$ and $\Delta G^\circ > 0$, so the reaction is thermodynamically favored.(D)The cell has $E^\circ_{cell} = +3.12\ \text{V}$ and $\Delta G^\circ < 0$, so the reaction is thermodynamically favored.

27. **2. [Skill: 1B | Topic: 9.9]** A student proposes an electrochemical cell based on the overall reaction $Cu^{2+}(aq) + 2Cl^-(aq) \rightarrow Cu(s) + Cl_2(g)$ The student consults a standard reduction potential table and finds: - $Cu^{2+}(aq) + 2e^- \rightarrow Cu(s)$, $E^\circ = +0.34\ \text{V}$ - $Cl_2(g) + 2e^- \rightarrow 2Cl^-(aq)$, $E^\circ = +1.36\ \text{V}$ Which statement best describes the cell under standard conditions?

(A)The cell is galvanic because $E^\circ_{cell} = +1.70\ \text{V}$, so $\Delta G^\circ < 0$.(B)The cell is galvanic because $E^\circ_{cell} = +1.02\ \text{V}$, so $\Delta G^\circ < 0$.(C)The cell is electrolytic because $E^\circ_{cell} = -1.02\ \text{V}$, so $\Delta G^\circ > 0$ and an external potential of at least $1.02\ \text{V}$ is required to drive the reaction.(D)The cell is electrolytic because $E^\circ_{cell} = -1.70\ \text{V}$, so $\Delta G^\circ < 0$.

28. **1. [Skill: 2.A | Topic: 9.11]** A student electroplates a metal spoon by reducing $Ag^+(aq)$ to $Ag(s)$ in an electrolytic cell. The cell operates at a constant current of 2.50 A for 20.0 minutes. Assume 100% current efficiency. Relevant half-reaction: $Ag^+(aq) + e^- \rightarrow Ag(s)$ Which of the following is the best estimate of the mass of silver deposited on the spoon? (A) 0.0556 g (B) 1.68 g (C) 3.35 g (D) 6.70 g

(A)0.0556 g(B)1.68 g(C)3.35 g(D)6.70 g

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