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Quizzes > Science > Chemistry

Electrolysis & Electrolytic Cell Quiz: Take the Challenge!

Think you can ace these electrolysis practice problems? Dive in and test your knowledge!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration of electrolytic cell flasks electrodes wires lightning bolt on coral background for electrolysis quiz

Are you ready to tackle the secrets of electrolysis and electrolytic cell design? Our Electrolysis & Electrolytic Cell Quiz: Test Your Skills is crafted for curious minds like yours, offering a mix of electrolysis practice problems and thought-provoking electrolytic cell questions. Whether you're preparing for an electrochemical cell test or just brushing up on fundamentals, this free, interactive electrolysis quiz will challenge and inspire you. Delve deeper with our electrochemistry test for a broader view of redox reactions, or review key concepts in electrolyte and nonelectrolyte solutions to strengthen your understanding. Jump in now to test your skills, learn something new, and boost your confidence - start the challenge today!

What is electrolysis?
The mixing of electrolytes to form a solution.
The generation of electricity from a chemical reaction.
The spontaneous redox reaction in a galvanic cell.
The decomposition of a compound by an electric current.
Electrolysis is the process where an external electric current causes a non-spontaneous chemical decomposition. It is essentially forced redox using electricity rather than generating it. This distinguishes it from galvanic cells, which produce electricity from spontaneous reactions. Wikipedia: Electrolysis
In an electrolytic cell, which electrode is connected to the positive terminal of the external power supply?
Both electrodes
Anode
Neither electrode
Cathode
In an electrolytic cell, the anode is connected to the positive terminal and attracts anions. This is opposite to a galvanic cell, where the anode is negative. The positive connection forces oxidation at that electrode. LibreTexts: Electrolytic Cells
What substance is produced at the cathode during electrolysis of molten sodium chloride?
Hydrogen gas
Chlorine gas
Sodium chloride
Sodium metal
In molten sodium chloride, Na+ ions migrate to the cathode and gain electrons to form sodium metal. This is a reduction process. Chloride ions are oxidized at the anode to form chlorine gas. Wikipedia: Electrolysis of molten salts
Which term describes the negatively charged electrode in electrolysis?
Electrode
Cathode
Ion
Anode
In electrolysis, the cathode is the negatively charged electrode where reduction occurs. It attracts cations from the electrolyte. The anode is positive and attracts anions. LibreTexts: Cathode and Anode
In the electrolysis of an aqueous copper(II) sulfate solution with inert electrodes, what deposits on the cathode?
Oxygen gas
Copper metal
Copper sulfate
Sulfur
Copper(II) ions in solution are reduced at the cathode to form metallic copper deposits. The inert electrodes do not participate chemically aside from conducting electricity. The sulfate ion remains in solution. Wikipedia: Electroplating
During the electrolysis of water using inert electrodes, which gas evolves at the cathode?
Chlorine gas
Hydrogen gas
Nitrogen gas
Oxygen gas
Water molecules are reduced at the cathode, producing hydrogen gas and hydroxide ions. Hydrogen has a lower reduction potential than oxygen in this context. Oxygen evolves at the anode instead. Khan Academy: Electrolysis of water
What is the primary role of the electrolyte in an electrolytic cell?
To conduct electricity via ion movement
To prevent redox reactions
To supply the external voltage
To generate electrons at electrodes
An electrolyte provides mobile ions that carry charge through the solution, completing the electrical circuit. It does not generate electrons; the power supply does that. Without an electrolyte, current cannot flow between electrodes in the cell. LibreTexts: Electrolytes
Which of the following is NOT a product of electrolysis of water?
Hydrogen peroxide
Hydroxide ions
Hydrogen gas
Oxygen gas
Standard water electrolysis produces hydrogen at the cathode and oxygen at the anode, along with hydroxide ions in alkaline cells. Hydrogen peroxide is not a primary product except in specialized cell designs. No peroxide accumulates under normal conditions. Wikipedia: Electrolysis of water
How many moles of electrons are needed to reduce one mole of aluminum ions (Al3+) to metallic aluminum?
1
0.5
3
2
The reduction half-reaction for Al3+ is Al3+ + 3 e- ? Al. Therefore, three moles of electrons are required to reduce one mole of aluminum ions. This stoichiometry is central to Faraday's laws in aluminum electrolysis. LibreTexts: Faraday's Laws
The numerical value of the Faraday constant (amount of charge per mole of electrons) is closest to:
96,485 C/mol
1.602×10?¹? C
1 F
8,314 J/(mol·K)
The Faraday constant is defined as the charge of one mole of electrons, approximately 96,485 coulombs. It links the macroscopic charge passed in electrolysis to moles of electrons transferred. It is different from the gas constant R or elementary charge. Wikipedia: Faraday constant
What does the term 'overpotential' refer to in electrolysis?
The extra voltage required beyond the thermodynamic potential
The minimum potential needed for electrode passivation
The potential drop across the solution resistance
The maximum current density achievable
Overpotential is the additional voltage required to drive an electrochemical reaction at a desired rate, exceeding the theoretical electrode potential. It arises from kinetic barriers, mass transport, and electrode surface effects. Overpotential reduces energy efficiency by requiring extra energy input. LibreTexts: Overpotential
In the electrolysis of aqueous sodium chloride using inert electrodes, which species is produced at the cathode?
Hydrogen gas
Sodium metal
Chlorine gas
Sodium hydroxide
In aqueous NaCl electrolysis, water is preferentially reduced at the cathode rather than sodium ions, producing hydrogen gas and hydroxide ions. Sodium metal cannot form in water due to its rapid reaction. Chlorine evolves at the anode instead. Britannica: Chloralkali process
Which factor does NOT affect the mass of substance deposited during electrolysis according to Faraday's laws?
Total charge passed
Valency of the ion
Electrode surface area
Time of electrolysis
According to Faraday's laws, mass deposited is proportional to charge passed and inversely proportional to ion valency and molar mass. Electrode surface area influences rate but not total mass when charge is fixed. Time and current determine total charge. LibreTexts: Faraday's Laws
In an electrolytic cell, electrons flow externally from:
Electrode to salt bridge
Anode to cathode
Cathode to anode
Salt bridge to solution
In any electrochemical cell, electrons travel from the anode (where oxidation occurs) through the external circuit to the cathode (where reduction occurs). This direction is the same in both galvanic and electrolytic cells, even though polarity labels differ. It completes the circuit for the redox process. LibreTexts: Electron Flow in Cells
What is Coulombic efficiency in the context of electrolysis?
Conductivity of electrolyte
Total energy efficiency of cell
Overpotential value
Ratio of actual to theoretical mass deposition
Coulombic efficiency measures the fraction of electric charge that contributes to the desired chemical transformation versus side reactions. It is calculated as the actual mass deposited divided by the theoretical mass predicted by charge passed. High coulombic efficiency indicates minimal side reactions. ECS Interface: Coulombic Efficiency
Which cell notation correctly represents copper plating from Cu2+ solution using inert electrodes?
Pt(s)|Cu(s)||Cu2+(aq)
Pt(s)|Cu2+(aq)||Cu(s)
Cu2+(aq)|Pt(s)||Cu(s)
Cu(s)|Cu2+(aq)||Pt(s)
Cell notation lists the anode on the left and the cathode on the right, with phase boundaries. In copper plating, an inert platinum anode is in Cu2+ solution, and metallic copper forms on the cathode. The correct representation is Pt(s)|Cu2+(aq)||Cu(s). LibreTexts: Cell Notation
What is the overall cell reaction during the electrolysis of molten magnesium chloride?
MgCl2 ? Mg + Cl2
Mg + Cl2 ? MgCl2
MgCl2 + 2 e- ? Mg + 2 Cl-
2 MgCl2 ? 2 Mg + 2 Cl2
Molten MgCl2 undergoes reduction at the cathode forming Mg and oxidation at the anode forming Cl2. Combining these half-reactions gives MgCl2 ? Mg + Cl2. This overall reaction reflects decomposition of the salt. LibreTexts: Electrolysis of Molten Salts
High current densities in electrolytic cells often lead to which issue?
Activation polarization
Electrode passivation
Concentration polarization
Thermal runaway
At high current densities, mass transport of reactants can't keep up with the reaction rate, causing concentration gradients. This leads to concentration polarization, which increases overpotential. It reduces cell efficiency and can change product distribution. ScienceDirect: Concentration Polarization
In the chlor-alkali process, which type of membrane allows selective passage of ions to separate chlorine and hydroxide?
Porous ceramic membrane
Anion exchange membrane
Polymer electrolyte membrane
Cation exchange membrane
Cation exchange membranes permit positive ions like Na+ to pass while blocking anions Cl- and OH-. This separation prevents product mixing and allows pure streams of chlorine and sodium hydroxide. Anion exchange membranes work oppositely. Wikipedia: Chloralkali process
When electrolyzing a solution containing Cu2+ and Fe2+ ions, which metal will deposit first at the cathode?
Copper
Iron
No deposition occurs
Both deposit simultaneously
Copper has a higher (more positive) reduction potential than iron, so Cu2+ ions are reduced before Fe2+. Fe deposition requires a larger negative potential. As long as Cu2+ remains in solution, only copper plates out. LibreTexts: Standard Reduction Potentials
What mass of chlorine gas (Cl2) is theoretically produced by passing 193,000 C of charge through molten NaCl?
70.9 g
17.7 g
141.8 g
35.45 g
Cl2 formation requires two electrons per molecule: 2 Cl- ? Cl2 + 2 e-. A Faraday (96,485 C) corresponds to 1 mol e-; 193,000 C equals ~2 mol e-, yielding 1 mol Cl2 (70.9 g). LibreTexts: Faraday's Laws
Gas bubble adhesion on electrode surfaces in electrolysis increases overpotential because it:
Lowers the cell voltage
Decreases effective electrode area
Enhances ion mobility
Increases electron transfer rate
Adhering gas bubbles block active electrode sites, reducing the effective surface area. This increases current density at the remaining area and thus raises overpotential. It also impedes mass transport of reactants to the electrode. ScienceDirect: Gas Evolution
A polarization curve in electrolysis typically plots:
Concentration vs distance
Potential vs current density
Current density vs electrode material
Cell voltage vs time
A polarization curve shows how the electrode potential varies with current density. It highlights activation, ohmic, and concentration polarization regions. It is used to analyze cell performance and efficiency. ECS: Polarization Curves
In a mixed electrolyte containing both chloride and nitrate ions, which species is preferentially oxidized at the anode in aqueous electrolysis?
Chloride to chlorine gas
Water to oxygen gas
Nitrate to nitrite
Hydroxide to ozone
Chloride ions have a lower oxidation potential than water and nitrate ions, so they oxidize preferentially to form chlorine gas. Nitrate oxidation requires much higher potentials and typically does not occur under standard conditions. This selectivity is exploited in chlor-alkali processes. Electrochimica Acta: Anodic Oxidation
Which modification is most effective for improving current efficiency in an industrial aluminum electrolytic cell?
Increasing cell voltage significantly
Using a porous graphite cathode
Adding cryolite to lower the melting point
Decreasing cell temperature drastically
Adding cryolite reduces the melting point and viscosity of the alumina bath, decreasing ohmic losses and side reactions. This results in higher current efficiency and lower energy consumption. Simply raising voltage or drastic cooling can harm efficiency or inhibit proper electrode reactions. Alcoa: Aluminum Smelting
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Study Outcomes

  1. Explain Fundamentals of Electrolysis -

    Explain how electrical energy drives non-spontaneous chemical reactions by identifying key components and processes in an electrolytic cell.

  2. Solve Electrolysis Practice Problems -

    Solve calculations involving the mass of deposited substances, required current, and duration of electrolysis to reinforce quantitative skills.

  3. Predict Electrode Products -

    Predict the species produced at the cathode and anode based on electrolyte composition and cell conditions.

  4. Differentiate Electrolytic and Galvanic Cells -

    Differentiate between cell setups to recognize spontaneous versus non-spontaneous reactions and the direction of electron flow.

  5. Interpret Electrochemical Cell Diagrams -

    Interpret cell notation and diagrams to visualize reaction mechanisms, ion movement, and electrode functions.

  6. Evaluate Efficiency of Electrolytic Processes -

    Evaluate factors such as overpotential and current efficiency to understand practical limitations in electrolysis applications.

Cheat Sheet

  1. Fundamental Principles of Electrolysis -

    Electrolysis and electrolytic cell reactions rely on Faraday's laws, which relate the amount of substance liberated at each electrode to the total electric charge passed (Q = It). For example, passing 96 500 C (one Faraday) through molten NaCl yields 1 mol of Na metal and 1 mol of Cl₂ gas. Remember: "Charge in, moles out" is your mnemonic for mass - charge calculations in an electrochemical cell test.

  2. Electrode Roles and Notation -

    In any electrolytic cell, the cathode is where reduction occurs and cations migrate, while the anode is where oxidation occurs and anions move. A handy mnemonic is "Red Cat, An Ox" to distinguish reduction at the cathode and oxidation at the anode (IUPAC convention). When sketching diagrams for an electrolysis quiz, always label electrodes, cell compartments, and the external power source.

  3. Predicting Reaction Products -

    Use standard reduction potentials and the reactivity series to forecast which species will be discharged at each electrode (e.g., in aqueous solutions, H₂ or O₂ often form before less favorable metal ions). For instance, in an aqueous CuSO₄ solution, Cu²❺ reduces to Cu(s) at the cathode (E°=+0.34 V), while water oxidizes to O₂ at the anode (E°=+1.23 V). Practice with targeted electrolytic cell questions to build confidence in selecting the thermodynamically favored pathways.

  4. Quantitative Calculations -

    Apply Q = It along with Faraday's constant (F = 96 500 C mol❻¹) to compute masses or volumes of gases produced; for example, mass (m) = (Molar mass × I × t)/(nF). If 2 A flows for 1800 s through molten MgCl₂ (n=2), the moles of Mg deposited are (2×1800)/(2×96 500)≈0.0186 mol. Tackling electrolysis practice problems sharpens calculation speed and accuracy.

  5. Real-World Factors: Overpotential & Efficiency -

    Actual electrolytic cells incur overpotential losses due to kinetics and resistive heating, lowering the theoretical yield; this is why industrial processes often run at higher voltages. For example, chlorine evolution in brine electrolysis requires extra voltage to overcome overpotential at the anode. Keep these factors in mind when reviewing for an electrochemical cell test to connect theory with practical applications.

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