Electrochemistry Practice Test

These questions are part of the practice quiz. Start practicing

• Which statement best describes how cyclic voltammetry identifies a reversible redox couple?
• In Sn + 2 HCl → SnCl2 + H2, which species is reduced?
• Under what condition does the limiting current i_L occur?
• How does overpotential affect the observed cell potential during electrolysis versus galvanic operation?
• What role does a salt bridge play in an electrochemical cell, and what would happen if it were removed?
• What does the reaction quotient Q represent in the Nernst equation?
• Which statement best describes the Fe3+/Fe2+ standard potential significance?
• If E°cell > 0, what can be said about spontaneity and ΔG under standard conditions?
• In a concentration cell with identical redox couples on both sides, what determines the sign of Ecell?
• In relation to reference electrodes, the saturated calomel electrode (SCE) is widely used in labs because of stability. What is its approximate potential relative to the standard hydrogen electrode at 25°C?
• In each half-cell of an electrochemical cell, which process occurs at the anode and which at the cathode?
• In a concentration cell at 25°C using the same half-reaction in both electrodes, what happens to Ecell when the two ion concentrations become equal?
• Which statement best defines the standard electrode potential E° and its relation to Gibbs free energy change for a redox couple?
• In electrolytic deposition, which quantity is directly proportional to the total charge passed through the circuit?
• What is E° for the cell Fe | Fe2+ (1.0 M) || Zn2+ (1.0 M) | Zn, given E°(Zn) = -0.76 V and E°(Fe) = -0.44 V, when Zn is the cathode?
• Why is the standard state used in electrochemical problems?
• Which species will oxidize Cr2+ (E°red = -0.407) but not Mn2+ (E°red = +1.224)?
• Which species acts as the reducing agent in the reaction between hydrazine and chlorate in basic solution?
• In the Nernst equation, Ecell is related to which quantity?
• In the reaction Ga(l) + Br2(l) → GaBr3(s), which species acts as the oxidizing agent?
• What does Q represent in Faraday's law for electrolysis calculations?
• Which statement about salt bridges in electrochemical cells is true?
• Why are activities used instead of concentrations in standard potential calculations?
• In a diffusion-controlled current transient after a potential step, the current decays proportional to which function of time?
• Using standard potentials, what is the largest approximate E° value that can be achieved when two half-cell reactions are combined to form a battery?
• In the balanced equation 2 Al(s) + 3 Ni2+(aq) → 2 Al3+(aq) + 3 Ni(s), what is the coefficient of Al(s)?
• What is a Pourbaix diagram and what information does it convey?
• Which is the weakest reducing agent among Li+, Li, F-, F2?
• In a redox reaction, how is the number of electrons transferred (n) determined from balanced half-reactions?
• In the cell Pt | H2 | H+ || Pb2+ | Pb, is the cell galvanic or electrolytic, and what species is produced at the cathode?
• What does E°cell represent in electrochemistry?
• What are the main mechanisms by which mass transport occurs in electrochemical cells?
• In the spontaneous redox reaction X(s) + Y2+(aq) ⇌ X2+(aq) + Y(s), when [X2+] and [Y2+] are equal, the cell potential is positive. If [X2+] = 10 × [Y2+], how will Ecell change?
• How is E°cell computed from a standard reduction potential table?
• In an electrochemical cell, which electrode is the site of oxidation?
• How does increasing the dissolved oxygen partial pressure, pO2, at fixed pH affect the electrode potential of the O2/H2O couple?
• What are the conventional standard states for solutes and gases in electrochemical data?
• What is the standard value of Faraday's constant used in electrochemistry?
• In a salt-bridge–compatible cell, which direction do ions move in the salt bridge during a galvanic reaction?
• Compute ΔG° for n=2, E°cell=0.40 V.
• For the H+/H2 couple at 25°C with E° = 0 V, what is the electrode potential at pH 7?
• In Li-ion batteries, what is the role of the SEI layer?
• Which statement about coulometry is correct?
• Which statement correctly describes the spontaneity criterion for a galvanic cell?
• In the galvanic cell Pt | Fe2+/Fe3+ || Ag+/Ag, how many electrons are transferred in the balanced overall reaction?
• In SnCl2, what is the oxidation state of tin?
• What is the overall discharge reaction for a lead-acid battery?
• If Cu2+/Cu (E°red = +0.34 V) and Fe2+/Fe (E°red = -0.44 V) are connected as a galvanic cell, which arrangement yields a positive E°cell?
• For a redox reaction that is non-spontaneous, which of the following is true under standard conditions?
• State Randles-Sevcik equation for the peak current in a diffusion-controlled CV at 25°C.
• Using the Nernst equation with E° = 0.34 V, n = 2, and [Cu2+] = 0.01 M, what is the cell potential for Cu2+/Cu at 25°C?
• What is the Tafel region in electrode kinetics, and what information does the Tafel slope provide?
• For a Daniell cell (Zn|Zn2+||Cu2+|Cu), what is the standard cell potential E°cell given E°(Zn2+/Zn) = -0.76 V and E°(Cu2+/Cu) = +0.34 V?
• In electroplating, how does electrode potential influence the quality and composition of the deposited coating?
• How is the equilibrium constant K related to E° for a redox reaction that transfers n electrons?
• In the balanced acidic equation for Cl2(g) + S2O3^2−(aq) → Cl−(aq) + SO4^2−(aq), what is the coefficient of SO4^2−?
• Which species will reduce Ag+ but not Fe2+?
• Which of the following correctly states the potential of the SCE relative to the SHE at 25°C?
• Define corrosion potential and describe its significance for metal corrosion in an electrolyte.
• Determine the mass of copper deposited when 2.0 A of current is passed for 30 minutes from a Cu2+ solution (M = 63.55 g/mol, n = 2).
• What is the standard hydrogen electrode (SHE) and its significance in electrochemistry?
• Explain how the Nernst equation reduces to E = E° − (0.05916/n) log Q at 25°C.
• If a galvanic cell has E°cell = 0.54 V and transfers 3 electrons (n = 3), what is ΔG° for the reaction?
• In shorthand notation for electrochemical cells, which component corresponds to the anode?
• What is the role of the standard hydrogen electrode in defining standard reduction potentials?
• Explain the concept and purpose of electrochemical impedance spectroscopy (EIS).
• How is the standard free energy change ΔG° related to E°cell?
• Which redox pair cannot be used to make a voltaic cell?
• A half-reaction has E° = +0.80 V. What does this indicate about the tendency of the species to gain electrons?
• In the cell Mg(s) | Mg2+(aq) || Au+(aq) | Au(s), what is the cathode and what is the cell type?
• According to the standard activity series, would solid nickel be readily oxidized in an aqueous sodium sulfate solution?
• To raise the Nernst-predicted cell potential, which combination is effective?
• Overpotential is defined as what, and what are its three main components?
• What is the standard reduction potential of the hydrogen couple H+/H2 at standard conditions?
• In the shorthand notation for galvanic cells, which side corresponds to the anode?
• In the displacement reaction Ag+ + Cu → Cu2+ + Ag, which statement is correct?
• Provide an example of a redox couple that can serve as a pH sensor electrode and describe its measured relationship to pH.
• Which expression correctly relates ΔG° to E° and n?
• What is cathodic protection and give a basic mechanism?
• Differentiate between galvanic (voltaic) cells and electrolytic cells in terms of energy flow and external power source.
• What is the significance of the standard state (1 M, 1 atm, 25°C) in electrochemistry?
• Differentiate coulombic efficiency and energy efficiency in rechargeable batteries.
• What is the standard emf of the cell Cu(s) | Cu2+(aq) || Au+(aq) | Au(s)?
• Which expression gives the cell potential for a concentration cell using the same redox couple in both half-cells but different concentrations at 25°C?
• In the Nernst equation, what does activity represent, and why are activities used instead of concentrations?
• In non-aqueous solvents, redox potentials can shift due to which factors?
• What is a diffusion layer in electrochemical cells and why is its thickness important?
• How does increasing the scan rate affect capacitive current relative to faradaic current during cyclic voltammetry?
• If diffusion layer thickness δ increases, what happens to i_lim?
• How many electrons are transferred per formula unit in the redox couple Al + Ni2+ → Ni + Al3+?
• In a galvanic cell consisting of Cu2+/Cu and Zn2+/Zn, what is the overall reaction and is E°cell positive or negative?
• In the zinc/copper redox reaction, which species is oxidized?
• If E°cell > 0, what can be said about the spontaneity of the reaction as written in a galvanic cell?
• Which form of the Nernst equation correctly shows temperature dependence for non-standard conditions?
• Identify a redox couple that exhibits diffusion-controlled, reversible cyclic voltammetry with a peak current proportional to the square root of the scan rate.
• How does temperature affect E° and K for a redox couple?
• Give the expression for the Gibbs free energy change for an electrochemical cell in terms of E°cell and nF.
• Which equation correctly relates ΔG° and E°cell under standard conditions?
• What is the standard reduction potential defined relative to?
• For the reaction 2H+ + 2e− → H2, what is E° at 25°C?
• In the reaction Cl2(g) + S2O3^2−(aq) → Cl−(aq) + SO4^2−(aq) in acidic solution, which species is the reducing agent?
• Using Faraday's laws, what is the mass of copper deposited (n=2) when Q = 50,000 C?
• Which is the oxidation half-reaction for Mn in Mn(s) → Mn2+(aq) + 2e-?
• Which is the correct cell notation for a galvanic cell with a zinc electrode in Zn(NO3)2 and a silver electrode in AgNO3, with a salt bridge containing aqueous KNO3?
• In cyclic voltammetry, what does a larger peak-to-peak separation ΔEp indicate?
• In FeO(aq) + V2O5(aq) → Fe2O3(aq) + VO(aq), which species acts as the reducing agent?
• In the reaction 2 Fe2+(aq) + H2O2(aq) → 2 Fe3+(aq) + 2 OH−(aq), which species is the oxidizing agent?
• What is a reference electrode and why is it necessary in electrochemistry experiments?
• How does the AgCl/Ag(s) electrode potential depend on chloride concentration?
• What is the standard cell potential E°cell for the Daniell cell Zn(s) | Zn2+ (1 M) || Cu2+ (1 M) | Cu(s) at standard conditions?
• Which expression gives the diffusion-limited current for a planar electrode with semi-infinite diffusion, assuming surface concentration is zero?
• How does pH affect the potential of the H+/H2 couple at 25°C?
• What is the standard reduction potential for the hydrogen half-reaction 2H+ + 2e- ⟶ H2 under standard conditions?
• A displacement reaction occurs at a metallic electrode in a solution containing Cu2+ and Zn2+. If Zn is more reactive, which species is reduced and which is oxidized at the electrode?
• What is the standard potential for the Fe3+/Fe2+ couple relative to SHE?
• If E°cell is positive, what is the sign of ΔG° at 25°C?
• In the same cell, which species is reduced at the cathode?
• Consider the skeletal equation Mn(s) + Ti2+(aq) → Mn2+(aq) + Ti(s). What is the proper shorthand notation (cell diagram) for this reaction?
• In cyclic voltammetry, how can you distinguish a reversible redox couple from an irreversible one?
• In the reaction Mn(s) + Ti2+(aq) → Mn2+(aq) + Ti(s), which species is reduced?
• If a redox reaction is non-spontaneous, what can be said about K?
• How do non-ideal activity coefficients affect standard electrode potentials (E°)?
• What factor is most directly altered by salt concentration in an aqueous solution to affect electrode potentials, and how is it accounted for?
• In a potentiometric titration, what determines the end-point potential?
• In a diffusion-controlled system following a potential step, which expression correctly represents the Cottrell current i(t)?
• Which framework is used to account for non-ideality in activity coefficients at moderate ionic strengths?
• Between a metal with a higher standard reduction potential and a metal with a lower one, which is reduced at the cathode?
• What constitutes the standard state for a solute in electrochemical problems?
• What is the oxidation state of vanadium in V2O5?
• For the reaction Zn(s) + Cu2+(aq, 0.01 M) → Zn2+(aq, 0.10 M) + Cu(s), with E°cell = 1.10 V and n = 2, what is the cell potential under these nonstandard conditions?
• A reaction has E°cell = -0.25 V. Under standard conditions, is it spontaneous as written?
• For a redox couple with n electrons and standard potential E° = 0.50 V at 298 K, what is the approximate equilibrium constant K?
• How does a redox indicator function in electrochemical sensing?
• Under standard conditions, what is the standard electrode potential value for the standard hydrogen electrode (SHE)?
• Are metals at the bottom of the activity series the most easily oxidized?
• In standard cell notation, which side corresponds to the anode?
• In balancing the acidic solution half-reaction CN− → CNO−, what is the coefficient of CN−?
• Calculate E°cell for the galvanic cell Zn(s) | Zn2+(aq) || Cl-(aq) | AgCl(s) | Ag(s).
• For the cell with E°cell = 0.80 V transferring 3 moles of electrons, what is ΔG° at 25°C?
• What is the difference between formal potential and standard potential?
• What is the standard cell potential for the cell formed by H+ / H2 (E° = 0.00 V) and O2 / H2O (E° = +1.23 V)?
• A galvanic cell constructed from a Mg electrode in 1.0 M Mg(NO3)2 and a Ag electrode in 1.0 M AgNO3 at 25°C has which standard cell potential?
• Which expression correctly relates deposited mass to charge for a redox process?
• Define the limiting current in a fuel cell or electrode reaction and give a simple expression.
• What is a Tafel plot and how is its slope related to kinetics?
• A 3.7 amp current is passed through an electrolytic cell, and Al3+ is reduced to Al at the cathode. What mass of solid aluminum is produced after six hours?
• In the reaction 2Al(s) + 3Fe2+(aq) → 2Al3+(aq) + 3Fe(s), where do the electrons have the lowest free energy?
• In the galvanic cell Zn(s)│Zn2+(aq) || Ag+(aq)│Ag(s), which species is reduced at the cathode?
• If a cell's limiting current is i_L = nFADCC/δ and both A and δ are doubled, what happens to i_L?
• Which equation represents the Butler-Volmer equation for electrode kinetics, and what do i0, η, and α denote?
• In balancing redox equations in basic solution, which species are used to balance oxygen and hydrogen atoms?
• Which of the following is the strongest reducing agent given the standard reduction potentials Cu2+/Cu (+0.34 V), Ag+/Ag (+0.80 V), and Fe2+/Fe (-0.44 V)?
• In the transformation of thiosulfate to sulfate, what is the oxidation state change for sulfur in S2O3^2−?
• What best defines the standard reduction potential (E°)?
• If using the H+/H2 couple to estimate pH at a fixed state, which relation is typically used at 25 C?
• What is the effect on Ecell when product concentrations increase (assuming other factors fixed)?
• In the cell Pt | Fe2+/Fe3+ || Ag+/Ag, which species is oxidized at the anode?
• Silver plating on copper occurs when copper is oxidized and acts as the reducing agent. Which statement correctly describes the plating process?
• In the discharge of a lead-acid battery, what is the anode reaction?
• Explain the difference between a polarized potential and an open-circuit potential.
• In a classic Daniell cell, which electrode serves as the anode and which serves as the cathode during spontaneous operation?
• What is the effect of adding a supporting electrolyte in a redox experiment?
• An electrochemical cell comprises two half-cells joined by a wire and a salt bridge. Which statement best describes its function?
• Which statement correctly describes standard cell potentials E°cell?
• Which equation is used to calculate Ecell from E°cell and Q at 25°C?
• In balancing the reaction N2H4(g) + ClO3−(aq) → NO(g) + Cl−(aq) in basic solution, what is the smallest possible integer coefficient in front of ClO3−?
• Which relation describes how the peak current i_p scales with the scan rate v for a diffusion-controlled, reversible redox couple?
• What happens to the cell potential Ecell as the reaction quotient Q increases for a galvanic cell?
• In a working electrochemical cell, the cations in the salt bridge move toward the cathode.
• Which metals will react with 1 M H2SO4 to produce hydrogen gas?
• In a table of standard reduction potentials, the metals with lower free energies are located where?
• What is the spontaneity criterion for a galvanic cell based on E°cell?
• In the balanced reaction Ca2+ (aq) + C(s) + ClO2(g) → CaCO3(s) + ClO2− (aq) balanced in basic conditions, what is the oxidation state of carbon in CaCO3(s)?
• How does a glass electrode measure pH and what is its slope at 25°C?
• Which type of electrochemical cell generates electrical energy from a spontaneous redox reaction?
• What is the general expression to convert charge to moles of electrons?
• In a concentration cell based on the same redox couple, how does increasing temperature affect Ecell?
• What is the conventional standard temperature used for electrochemical data?
• What is the purpose of a reference electrode and give two common examples with typical potential values?
• In AlH3, what is the oxidation state of hydrogen?
• What is the equilibrium constant for the reaction Fe2+ + Ag+ ⇌ Fe3+ + Ag?
• Which equation correctly relates ΔG°, n, F, and E°cell?
• Under standard state conditions, what is the value of the reaction quotient Q in the Nernst equation?
• During the decomposition of cobalt(II) chloride, which element is oxidized?
• The peak current i_p in the Randles-Sevcik equation is related to the scan rate v in which way?
• For an irreversible CV, what is the general relation between peak potential E_p and scan rate v according to the Laviron equation?
• If a cell contains identical electrodes and only the ion concentrations differ between half-cells, what type of cell is it and how is its potential determined?
• In the reaction PbS(s) + O2(g) → SO2(g) + PbO2(s), which species is the oxidizing agent?
• Define coulombic efficiency in electrochemical synthesis.
• The Tafel slope is related to the transfer coefficient α by which statement?
• In a polyatomic ion, the sum of the oxidation numbers of all atoms equals what?
• Sorry, there seems to be a duplication in the previous question set. Please review the questions for balance and independence.
• For the reaction Al(s) + Ni2+(aq) → Ni(s) + Al3+(aq), which species represents the oxidation half-reaction?
• In a Pourbaix diagram, what are the typical axes and what does the diagram reveal about a metal’s stability?
• Why is an overpotential required in water electrolysis for hydrogen and oxygen evolution?
• In electroplating, how does applying too high a current density affect the metal deposit?
• In balancing the basic equation MnO4− + NO2− → MnO2 + NO3−, what is the coefficient of NO3−?
• Which statement correctly contrasts a galvanic cell with an electrolytic cell?
• In the context of batteries, what is the function of a separator?
• What is the standard emf for the cell formed by Cu2+/Cu as the anode and Ag+/Ag as the cathode?
• In the redox reaction Zn(s) → Zn2+(aq) + 2 e−, how many electrons are transferred, and what is the corresponding n value in ΔG° = -n F E°?
• Which term in the Butler-Volmer equation represents the exchange current density?
• Balance the redox equation MnO4− + Fe2+ in acidic solution using the half-reaction method.
• In the redox reaction Sn(s) + 2 HCl(aq) → SnCl2(aq) + H2(g), which element is oxidized?
• Under standard conditions, which set of conditions defines the standard electrode potential?
• In standard-state conventions for gases, what is the reference pressure?
• Which principle is used to estimate Ecell under nonstandard conditions based on concentrations?
• In cobalt phosphate CoPO4 (cobalt(III) phosphate), what is the oxidation state of phosphorus?
• Why does double-layer capacitance matter in fast electrochemical measurements?
• A lab measurement uses a Ag/AgCl reference electrode with 3.5 M KCl; what is the approximate potential vs SHE?
• If E°cell > 0, what can be said about the equilibrium constant K?
• What is the thermodynamic minimum cell potential for water electrolysis at standard conditions (25°C)?
• In a galvanic cell, which statement about oxidation and reduction is correct?
• In an electrolytic cell, what is the sign of Ecell under the applied conditions to drive the nonspontaneous reaction?
• Which approach is used to account for changes in activity coefficients due to ionic strength?
• In a galvanic cell, how can you increase the measured cell potential under nonstandard conditions?
• What is the overall reaction for the electrolysis of water with inert electrodes at standard conditions, neglecting overpotentials?
• Using the Nernst equation, calculate the cell potential for a two-electron transfer (n = 2) with E° = 1.10 V when Q = 1.0×10^-3.
• In the same reaction, what is the total number of electrons transferred?
• In a galvanic cell with Pt | Sn2+(aq) 0.10 M, Sn4+(aq) 0.0010 M || Ag+ 0.010 M | Ag, the electrons flow in the external circuit from
• In an electrolytic cell, the negative terminal is the cathode and is the site of the reduction half-reaction. Which alternative statement is true?
• In the Nernst equation for the reaction Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s), which expression correctly defines the reaction quotient Q?
• If a half-cell has E° = +0.80 V and the measured potential at a given condition is +0.60 V, what does this indicate about the reaction propensity under those conditions?
• Which type of electrode processes is described by the Butler-Volmer equation?
• In the Randles-Sevcik equation, which variable explicitly represents temperature?
• In cyclic voltammetry, what does a large peak-to-peak separation indicate about the reaction kinetics?
• Why do multi-electron transfers complicate interpretation of standard potentials?
• In the decomposition of cobalt(II) chloride, which element undergoes oxidation?
• If the total charge that passes is 964.85 C, how many moles of electrons are transferred?
• Which reference electrode has a standard potential closest to +0.197 V relative to the SHE?
• Define exchange current density i0 and describe how it is determined experimentally.
• Which statement best describes coulometry?
• Is ZnCO3(s) → ZnO(s) + CO2(g) a redox reaction?
• How does temperature affect the Nernst equation?
• In Mn3(PO4)2, what is the oxidation state of manganese?
• What is the general effect of complexing ligands on redox potentials, as illustrated by CN- complexes of iron?
• In the cell Cd(s) | CdSO4(aq) || Hg2SO4(aq) | Hg(l) | Pt(s), what is the cathode half-reaction?
• In a standard cell notation, which side represents the anode?