Galvanic (Voltaic) and Electrolytic Cells - AP Chemistry

A student sets up two half-cells, $\text{Zn}(s)|\text{Zn}^{2+}(aq)$ and $\text{Cu}^{2+}(aq)|\text{Cu}(s)$ , connected by a salt bridge and a wire that passes through a light bulb. When the circuit is completed, the bulb lights without any battery attached, and the zinc electrode gradually becomes thinner. Based on these observations, which statement best classifies the process and its defining feature?
Answer: The process is galvanic because it produces electrical energy from a spontaneous redox reaction. This question tests understanding of galvanic (voltaic) and electrolytic cells. In galvanic cells, spontaneous redox reactions produce electrical energy, while electrolytic cells require electrical energy input to drive nonspontaneous reactions. The key observation here is that the bulb lights without any external power source, indicating electrical energy is being produced by the cell itself, and zinc dissolving shows the reaction is proceeding spontaneously. This definitively identifies the cell as galvanic. A common misconception is that salt bridges supply electrons (choice D), but salt bridges only allow ion flow to maintain electrical neutrality—electrons flow through the external wire. To classify electrochemical cells: if the cell produces electricity without external power, it's galvanic; if it requires external power to function, it's electrolytic.
A student sets up two half-cells connected by a salt bridge and a wire: Fe(s) in FeSO $_4$ (aq) and Ag(s) in AgNO $_3$ (aq). The student measures a steady voltage with a voltmeter (no battery attached). When the wire is connected through a small motor, the motor turns briefly and the Ag electrode increases in mass. Which statement correctly classifies the process and identifies a defining feature?
Answer: It is a galvanic (voltaic) process, and it produces electrical energy from a spontaneous redox reaction. This question tests your understanding of galvanic (voltaic) and electrolytic cells. In galvanic cells, spontaneous redox processes release free energy, which is harnessed as electrical work, such as powering a motor or generating voltage. Electrolytic cells demand input of electrical energy to drive nonspontaneous reactions, like electrolysis. The direction of electron flow is determined by spontaneity: in galvanic cells, electrons move naturally toward the more positive potential, while in electrolytic cells, an external force dictates the flow. A tempting distractor is choice A, which wrongly labels it as electrolytic, based on the misconception that mass changes at electrodes always indicate a forced process. To distinguish between cell types, remember that if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
A student observes an electrochemical device in which two half-cells are connected by a salt bridge. The device is connected to an external power supply, and when the power supply is turned on, one electrode shows visible corrosion (loss of metal), while the other electrode becomes coated with metal. Which statement correctly classifies the process and identifies a defining feature?
Answer: It is an electrolytic cell because an external power source is used to drive the redox reaction, causing oxidation at one electrode and metal deposition at the other. This question tests understanding of galvanic (voltaic) and electrolytic cells. The external power supply driving the reaction identifies this as an electrolytic cell, where electrical energy forces a nonspontaneous redox reaction. At the anode (positive electrode), metal oxidizes and corrodes, while at the cathode (negative electrode), metal ions are reduced and deposit as solid metal. Choice B incorrectly assumes corrosion indicates spontaneity, but in this case, the power supply forces the oxidation. The strategy is that when an external power source drives oxidation at one electrode and reduction at another, the cell is electrolytic.
An object is electroplated with nickel by placing it in a NiSO $_4$ (aq) solution and connecting it to the negative terminal of a DC power supply. A Ni(s) strip is connected to the positive terminal. Nickel metal builds up on the object only while the power supply is on. Which statement correctly classifies the process and its defining feature?
Answer: Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells feature spontaneous redox processes that produce electrical energy, with electrons flowing naturally due to a favorable potential difference. Electrolytic cells, on the other hand, use an external power source to drive nonspontaneous reactions, compelling electron movement against the potential gradient. The core distinction lies in whether the reaction's spontaneity allows energy release or necessitates energy input, which governs the electron flow direction. Choice B is a misleading option, incorrectly identifying it as galvanic with spontaneous energy production, based on the misconception that metal deposition always indicates a spontaneous process without considering the need for external power. To distinguish between cell types, remember: if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
Two half-cells are connected with a salt bridge: Sn(s) in SnCl $_2$ (aq) and Pb(s) in Pb(NO $_3$ ) $_2$ (aq). A student connects the electrodes through a wire and observes that the voltmeter reads approximately 0 V and no sustained current flows unless a battery is connected in series. With the battery connected, the Pb electrode gains mass. Which statement best describes the process occurring when the battery is connected?
Answer: Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells operate via spontaneous redox reactions that yield electrical energy, enabling electron flow without external intervention. In electrolytic cells, nonspontaneous reactions are forced by supplying electrical energy, directing electrons to achieve the desired chemical change. Spontaneity determines if the cell outputs energy (galvanic) or requires input (electrolytic), thus controlling the electron movement pathway. Choice A is a tempting distractor, labeling it as galvanic with spontaneous energy production, rooted in the misconception that near-zero voltage always means a spontaneous cell when in fact it indicates nonspontaneity here. To distinguish between cell types, remember: if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
Two inert Pt electrodes are placed into a beaker of molten NaCl. The electrodes are connected to a DC power supply, and bubbles form at one electrode while a shiny metallic deposit forms at the other. When the power supply is turned off, the reactions stop. Which statement correctly classifies the process and identifies a defining feature?
Answer: It is an electrolytic process, and it requires an external power source to force a nonspontaneous reaction. This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells harness spontaneous reactions to generate electricity, with the reaction proceeding naturally and producing a positive cell potential. Electrolytic cells, however, involve nonspontaneous reactions that absorb energy, necessitating an external voltage to overcome the energy barrier. Electron movement in galvanic cells is driven by the reaction's spontaneity from anode to cathode, whereas in electrolytic cells, the external source forces electrons from cathode to anode in the cell's perspective. A tempting distractor is choice A, which misclassifies it as galvanic, stemming from the misconception that any redox reaction producing visible products like deposits or gases must be spontaneous. To distinguish between cell types, remember that if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
Molten NaCl is placed in a container with two inert electrodes connected to a DC power supply. When the power supply is turned on, bubbles form at one electrode and a silvery metal forms at the other. The process stops when the power supply is disconnected. Which statement correctly classifies the process and its defining feature?
Answer: Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells rely on spontaneous redox reactions to generate electrical energy, with electrons moving voluntarily from higher to lower potential without external aid. Electrolytic cells, however, drive nonspontaneous reactions by inputting electrical energy from an outside source, overriding the natural tendency and directing electron flow. The energy flow—output in galvanic versus input in electrolytic—directly influences the direction and feasibility of electron movement in the circuit. Choice D is a common distractor, wrongly labeling it as electrolytic with a spontaneous reaction, based on the misconception that all processes producing visible products like gases or metals must be spontaneous regardless of energy input. To distinguish between cell types, remember: if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
A student places a spoon in a solution containing $\text{Ni}^{2+}(aq)$ and connects the spoon to one terminal of a battery. A nickel strip is connected to the other terminal. After several minutes with the battery connected, the spoon gains a shiny nickel coating. Which statement best classifies the process and its defining feature?
Answer: The process is electrolytic because an external power source is required to drive the redox reaction that plates nickel. This question tests understanding of galvanic (voltaic) and electrolytic cells. The battery connection is essential for nickel plating to occur, indicating that electrical energy input is required to drive this nonspontaneous electroplating process. In this electrolytic cell, the battery forces electrons to flow to the spoon (cathode), where Ni²⁺ ions are reduced to metallic nickel coating, while nickel metal is oxidized at the anode. Without the battery, nickel would not spontaneously plate onto the spoon. A misconception is that electrons move through the solution (choice D), but electrons always travel through the external circuit—ions carry charge in solution. To identify electrochemical cells: if a battery or power source is required for the desired reaction (like electroplating), it's electrolytic.
A student builds an electrochemical setup with two beakers connected by a salt bridge and a wire, but also connects a battery in series in the external circuit. The student notes that the battery is necessary to keep the reaction occurring; when the battery is removed, the reaction stops and the voltmeter reads approximately 0 V. Which statement correctly classifies the process occurring when the battery is connected and identifies a defining feature?
Answer: It is an electrolytic process, and it requires an external power source to force a nonspontaneous reaction. This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells generate electrical energy through spontaneous reactions, functioning independently of external sources. Electrolytic cells rely on external power to enforce nonspontaneous reactions, ceasing when disconnected. Spontaneity governs electron flow in galvanic cells, directing it naturally, whereas energy input in electrolytic cells compels the flow against spontaneity. A tempting distractor is choice A, which wrongly classifies it as galvanic, stemming from the misconception that adding a battery to any setup still allows for spontaneous energy production. To distinguish between cell types, remember that if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
A student uses a rechargeable lithium-ion battery to power a phone (discharging). During use, the battery provides electrical energy to the circuit without being connected to a charger. Which statement correctly classifies the process occurring during discharge and its defining feature?
Answer: Galvanic (voltaic) cell; a spontaneous redox reaction produces electrical energy in the external circuit This question tests your understanding of galvanic (voltaic) and electrolytic cells. In galvanic cells, spontaneous processes generate electrical energy, with natural electron flow. Electrolytic cells require external energy to drive nonspontaneous processes, forcing electron direction. This spontaneity-energy relationship distinguishes cells and determines electron movement. Choice C is a tempting choice, misclassifying it as galvanic needing power, based on the misconception that batteries always require external input even during discharge. To distinguish between cell types, remember: if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
A student is told that in a particular electrochemical setup, electrical energy must be supplied continuously; otherwise, the observed chemical change (metal deposition) stops and gradually reverses. No other quantitative information is provided. Which statement correctly classifies the setup and its defining feature?
Answer: Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction This question tests your understanding of galvanic (voltaic) and electrolytic cells. In galvanic cells, spontaneous processes generate electrical energy, with natural electron flow. Electrolytic cells require external energy for nonspontaneous processes, forcing direction. Spontaneity and energy flow differentiate, determining movement. Choice B is incorrect, labeling galvanic needing power, from misconception that reversal implies spontaneity. To distinguish between cell types, remember: if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
A student assembles an electrochemical cell with a Zn(s) electrode in ZnSO $_4$ (aq) and a Cu(s) electrode in CuSO $_4$ (aq), connected by a salt bridge and a wire. When the circuit is completed, a voltmeter reads a nonzero voltage without any battery attached, and the Cu electrode gains mass over time. Based on these observations, which statement correctly classifies the process and identifies a defining feature?
Answer: It is a galvanic (voltaic) process, and it produces electrical energy from a spontaneous redox reaction. This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells involve spontaneous redox reactions that release energy, converting chemical energy into electrical energy without needing an external power source. In contrast, electrolytic cells require an external power source to drive nonspontaneous reactions, using electrical energy to force chemical changes. In galvanic cells, electrons flow spontaneously from the anode to the cathode through the external wire, while in electrolytic cells, the power source pushes electrons in the opposite direction relative to spontaneity. A tempting distractor is choice A, which incorrectly classifies the process as electrolytic, based on the misconception that all cells requiring a salt bridge must be nonspontaneous and need external power. To distinguish between cell types, remember that if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
The same rechargeable lithium-ion battery is later connected to a wall charger. While charging, electrical energy is supplied to the battery, and the chemical changes reverse compared with discharge. Which statement correctly classifies the process occurring during charging and its defining feature?
Answer: Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells produce electricity from spontaneous reactions, electrons flowing spontaneously. Electrolytic cells use external power for nonspontaneous reactions, directing flow. Spontaneity and energy flow differentiate, governing electrons. Choice B is distractor, labeling galvanic with spontaneity, assuming reversal means spontaneity without power need. To distinguish between cell types, remember: if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
A student builds a cell using $\text{Mg}(s)|\text{Mg}^{2+}(aq)$ and $\text{Pb}^{2+}(aq)|\text{Pb}(s)$ half-cells connected by a salt bridge. The electrodes are connected to a small motor (no battery). When connected, the motor turns briefly and the magnesium electrode visibly corrodes. Which statement best classifies the process and its defining feature?
Answer: The process is galvanic because it converts chemical energy to electrical energy in a spontaneous reaction. This question tests understanding of galvanic (voltaic) and electrolytic cells. The motor turns without any external power source, demonstrating that the cell is producing electrical energy from a spontaneous redox reaction where magnesium (more active) reduces lead ions. The visible corrosion of magnesium confirms it's being oxidized while lead ions are reduced, and this spontaneous reaction generates the electrical energy that powers the motor. This is a classic galvanic cell converting chemical energy to electrical energy. A misconception is that the salt bridge pushes electrons (choice D), but salt bridges only allow ion flow—electrons travel through the external circuit to power the motor. Remember: if a cell can do electrical work (run a motor) without external power, it's galvanic; if it needs power input, it's electrolytic.
A student connects two electrodes in an aqueous solution to a DC power supply. The student notes that one electrode becomes coated with a metal that was previously present only as ions in solution, and the other electrode shows signs of dissolution or gas formation. Which statement correctly classifies the process and its defining feature?
Answer: Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction This question tests your understanding of galvanic (voltaic) and electrolytic cells. In galvanic cells, spontaneous reactions yield electricity, electrons flowing spontaneously. Electrolytic cells need input for nonspontaneous reactions, forcing electron direction. Energy flow and spontaneity differentiate, governing movement. Choice A is incorrect, labeling galvanic with spontaneity, assuming metal coating means spontaneous without power. To distinguish between cell types, remember: if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
In a lab demonstration, two graphite electrodes are placed into an aqueous solution of NaI. The electrodes are connected to a DC power supply. When the power supply is turned on, a brown color appears near one electrode and gas bubbles appear near the other. Which statement correctly classifies the process and identifies a defining feature?
Answer: It is an electrolytic cell because the reaction requires electrical energy from an external power source to proceed. This question tests understanding of galvanic (voltaic) and electrolytic cells. The DC power supply driving the reaction clearly identifies this as an electrolytic cell, where electrical energy forces the nonspontaneous electrolysis of NaI solution. At the anode, I⁻ is oxidized to I₂ (2I⁻ → I₂ + 2e⁻), producing the brown color, while at the cathode, water is reduced to H₂ gas (2H₂O + 2e⁻ → H₂ + 2OH⁻). Choice C incorrectly claims graphite electrodes cannot be used in electrolytic cells, but inert electrodes like graphite are commonly used in electrolysis. The strategy is that when a power supply is actively driving a reaction, the cell is electrolytic.
An object is electroplated with nickel by placing it in a NiSO $_4$ (aq) solution. The object is connected to the negative terminal of a power supply, a Ni(s) strip is connected to the positive terminal, and a visible Ni coating forms on the object only while the power supply is on. Which statement correctly classifies the process and identifies a defining feature?
Answer: It is an electrolytic process, and it requires an external power source to force a nonspontaneous reaction. This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells produce electrical energy from spontaneous reactions, with the cell potential being positive and no external input required. Electrolytic cells consume electrical energy to enable nonspontaneous reactions, often used in processes like plating or purification. Electron flow in galvanic cells is spontaneous from the oxidation to reduction site, but in electrolytic cells, it's imposed by the power source to reverse the natural tendency. A tempting distractor is choice B, which incorrectly identifies it as galvanic, arising from the misconception that metal deposition always results from a spontaneous reaction. To distinguish between cell types, remember that if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
A corrosion scientist demonstrates a simple cell by placing an iron nail and a copper strip into a saltwater-soaked paper towel so they are electrically connected through a wire. A small voltage is detected and the iron shows signs of oxidation over time without any external power source. Which statement correctly classifies the process and its defining feature?
Answer: Galvanic (voltaic) cell; a spontaneous redox reaction produces electrical energy in the external circuit This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells produce energy via spontaneous redox, electrons flowing naturally. Electrolytic cells force nonspontaneous reactions with external power, directing electrons. Spontaneity and energy flow differentiate, affecting electron movement. Choice B is distractor, labeling electrolytic with spontaneity, assuming oxidation signs mean spontaneous without power. To distinguish between cell types, remember: if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
A student connects two half-cells with a salt bridge: Cu(s) in CuSO $_4$ (aq) and Ag(s) in AgNO $_3$ (aq). Without any external power source, electrons flow through the wire from the Cu electrode toward the Ag electrode, and the Ag electrode gains mass. Which statement correctly classifies the cell and its defining feature?
Answer: Galvanic (voltaic) cell; a spontaneous redox reaction produces electrical energy in the external circuit This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells generate electricity from spontaneous reactions, electrons moving naturally. Electrolytic cells require external power for nonspontaneous reactions, controlling electron flow. Spontaneity and energy distinguish types, determining electron movement. Choice A is distractor, calling it electrolytic needing power, assuming mass gain requires force despite spontaneity. To distinguish between cell types, remember: if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.
A student places two graphite electrodes into an aqueous solution of CuCl $_2$ (aq) and connects the electrodes to a battery. During operation, copper metal plates onto one electrode and bubbles form at the other. No reaction is observed when the battery is disconnected. Which statement correctly classifies the process and identifies a defining feature?
Answer: It is an electrolytic process, and it requires an external power source to force a nonspontaneous reaction. This question tests your understanding of galvanic (voltaic) and electrolytic cells. In galvanic cells, spontaneous reactions liberate energy as electricity, with no need for external forcing. Electrolytic cells, conversely, use supplied electricity to compel nonspontaneous changes, such as decomposing compounds. Electron flow follows spontaneity in galvanic setups, from anode to cathode, but is reversed in electrolytic cells by the external power dictating the direction. A tempting distractor is choice A, which erroneously calls it galvanic, stemming from the misconception that bubble formation indicates energy production rather than consumption. To distinguish between cell types, remember that if electrical energy is produced, the cell is galvanic; if it must be supplied, the cell is electrolytic.

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