Galvanic (Voltaic) and Electrolytic Cells
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AP Chemistry › Galvanic (Voltaic) and Electrolytic Cells
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?
It is a galvanic (voltaic) process, and it operates only because the salt bridge supplies electrons to the circuit.
It is a galvanic (voltaic) process, and it requires an external power source to force a nonspontaneous reaction.
It is an electrolytic process, and it requires an external power source to force a nonspontaneous reaction.
It is an electrolytic process, and it produces electrical energy from a spontaneous redox reaction.
It is a galvanic (voltaic) process, and it produces electrical energy from a spontaneous redox reaction.
Explanation
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 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?
Electrolytic cell; a spontaneous redox reaction produces electrical energy in the external circuit
Galvanic (voltaic) cell; a spontaneous redox reaction produces electrical energy in the external circuit
Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction
Galvanic (voltaic) cell; the electrolyte provides electrons to the wire
Galvanic (voltaic) cell; an external power source is required to force electron flow
Explanation
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?
Electrolytic cell; a spontaneous redox reaction produces electrical energy in the external circuit
Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction
Galvanic (voltaic) cell; the salt bridge supplies electrons to keep the reaction running
Galvanic (voltaic) cell; a spontaneous redox reaction produces electrical energy in the external circuit
Electrolytic cell; the salt bridge is the power source that drives electron flow
Explanation
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 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?
Electrolytic cell; the electrolyte is the power source that drives electron flow
Electrolytic cell; a spontaneous redox reaction produces electrical energy in the external circuit
Galvanic (voltaic) cell; an external power source is required to force a nonspontaneous redox reaction
Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction
Galvanic (voltaic) cell; a spontaneous redox reaction produces electrical energy in the external circuit
Explanation
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.
A student connects an Fe(s) electrode in FeSO$_4$(aq) to a Ag(s) electrode in AgNO$_3$(aq) using a salt bridge and a wire. A voltmeter connected across the electrodes reads a steady nonzero voltage without any battery attached. Over time, Ag(s) mass increases and the Fe(s) electrode loses mass. Which statement correctly classifies the process and identifies a defining feature?
It is an electrolytic cell because deposition of Ag(s) at an electrode requires external electrical energy.
It is an electrolytic cell because the voltmeter reading shows that electrical energy is being consumed to drive the reaction.
It is an electrolytic cell because electrons flow through the salt bridge from one solution to the other.
It is a galvanic (voltaic) cell because the salt bridge acts as the power source for electron flow.
It is a galvanic (voltaic) cell because the reaction occurs spontaneously and generates electrical energy (a measurable voltage) without an external power source.
Explanation
This question tests understanding of galvanic (voltaic) and electrolytic cells. The voltmeter reads a nonzero voltage without any battery attached, which proves the cell is spontaneously generating electrical energy from the redox reaction between Fe and Ag⁺. In this galvanic cell, Fe oxidizes (Fe → Fe²⁺ + 2e⁻) at the anode while Ag⁺ is reduced (Ag⁺ + e⁻ → Ag) at the cathode, with electrons flowing through the external wire. Choice A incorrectly claims that a voltmeter reading shows energy consumption, but voltmeters measure potential difference without consuming significant energy. The key strategy is that if a cell generates measurable voltage without external power, it must be galvanic.
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?
It is a galvanic (voltaic) process, and it produces electrical energy from a spontaneous redox reaction.
It is an electrolytic process, and it produces electrical energy from a spontaneous redox reaction.
It is an electrolytic process, and it requires an external power source to force a nonspontaneous reaction.
It is a galvanic (voltaic) process, and it operates only because the salt bridge supplies electrons to the circuit.
It is a galvanic (voltaic) process, and it requires an external power source to force a nonspontaneous reaction.
Explanation
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 student observes that in an electrochemical cell, the reaction proceeds on its own once the circuit is closed, and the device can be used as a power source for a small calculator. No external battery is connected. Which statement correctly classifies the cell and its defining feature?
Electrolytic cell; a spontaneous redox reaction produces electrical energy in the external circuit
Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction
Galvanic (voltaic) cell; the salt bridge supplies electrons to keep the reaction running
Galvanic (voltaic) cell; an external power source is required to force a nonspontaneous redox reaction
Galvanic (voltaic) cell; a spontaneous redox reaction produces electrical energy in the external circuit
Explanation
This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells convert spontaneous redox to electrical energy, electrons moving naturally. Electrolytic cells force nonspontaneous redox with external energy, controlling path. This distinction affects classification and electron behavior. Choice B is tempting, labeling electrolytic with spontaneity, assuming powering devices means electrolytic. 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 laboratory demonstration, a student connects a galvanic cell to a second electrochemical cell using wires. The galvanic cell powers the second cell, causing metal to plate onto an electrode in the second cell. No wall outlet or battery is used. Which statement best describes the second cell while it is being powered by the first?
Galvanic (voltaic) cell; a spontaneous redox reaction produces electrical energy in the external circuit
Electrolytic cell; an external source of electrical energy is required to force a nonspontaneous redox reaction
Electrolytic cell; the salt bridge supplies electrons to keep the reaction running
Electrolytic cell; a spontaneous redox reaction produces electrical energy in the external circuit
Galvanic (voltaic) cell; an external power source is required to force a nonspontaneous redox reaction
Explanation
This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells harness spontaneous reactions to output electricity, electrons flowing voluntarily. Electrolytic cells input electricity to drive nonspontaneous reactions, compelling flow. This energy-spontaneity dynamic defines cell type and electron movement. Choice A is tempting, labeling galvanic with spontaneity, based on misconception that powering another cell makes the second spontaneous. 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 commercial alkaline battery powers a flashlight. As the battery discharges, chemical reactants inside the sealed cell are consumed and electrical energy is delivered to the circuit without any external power supply. Which statement correctly classifies the process and its defining feature?
Electrolytic cell; a spontaneous redox reaction produces electrical energy in the external circuit
Galvanic (voltaic) cell; the salt bridge supplies electrons to keep the reaction running
Galvanic (voltaic) cell; an external power source is required to force electron flow
Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction
Galvanic (voltaic) cell; a spontaneous redox reaction produces electrical energy in the external circuit
Explanation
This question tests your understanding of galvanic (voltaic) and electrolytic cells. Galvanic cells utilize spontaneous redox reactions to generate electrical energy, with electrons flowing freely from anode to cathode. Electrolytic cells demand an external power source to propel nonspontaneous reactions, reversing the natural electron flow. The interplay of spontaneity and energy flow differentiates the cells, determining if electrons move voluntarily or under compulsion. Choice D is an incorrect choice, classifying it as electrolytic with spontaneous energy production, stemming from the misconception that sealed systems like batteries must always require external power even when discharging spontaneously. To distinguish between cell types, remember: if electrical energy is produced, the cell is galvanic; if it must be supplied, 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?
Galvanic (voltaic) cell; a spontaneous redox reaction produces electrical energy in the external circuit
Electrolytic cell; the salt bridge supplies electrons to keep the reaction running
Electrolytic cell; an external power source is required to force a nonspontaneous redox reaction
Electrolytic cell; a spontaneous redox reaction produces electrical energy in the external circuit
Galvanic (voltaic) cell; an external power source is required to force a nonspontaneous redox reaction
Explanation
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.