Electrochemistry and Nernst Equation
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Questions and Answers

What gas is liberated at the cathode during the passage of current with CuSO4?

  • H2 (correct)
  • O2
  • Cl2
  • CO2

    • Which of the following is formed at the anode when current passes through CuSO4 solution?

  • Cl2 (correct)
  • Cu
  • O2
  • H2

    • What effect does CuSO4 have on the pH level of the solution?

  • Varies the pH
  • Has no effect on pH
  • Increases the pH
  • Decreases the pH (correct)

    • Which of the following statements is true about the liberation of gases during the electrolysis of CuSO4?

    <p>H2 reacts with oxygen to form water.</p> Signup and view all the answers

    What happens to hydrogen gas during the electrolysis of CuSO4?

    <p>It reacts with oxygen.</p> Signup and view all the answers

    What is the correct decreasing order of reducing power of the metals listed?

    <p>Ag &gt; Cr &gt; Al &gt; K</p> Signup and view all the answers

    How is the l0m (in S cm2 mol–1) for CH3COOH calculated based on the provided equations?

    <p>(x - y) + z</p> Signup and view all the answers

    Which option lists a possible l0m value for K2SO4 based on the given equations?

    <p>y = x - z</p> Signup and view all the answers

    Among the given metals, which has the lowest reducing power?

    <p>K</p> Signup and view all the answers

    Which of the following equations incorrectly represents the l0m values?

    <p>x + y + z</p> Signup and view all the answers

    Which salt solution will turn blue when a strip of Cu is placed in it?

    <p>Zn(NO3)2</p> Signup and view all the answers

    Which of the following reactions does not occur?

    <p>Cu + Fe2+ → Cu2+ + Fe</p> Signup and view all the answers

    What is the standard emf of the cell reaction Zn + Cu2+ → Zn2+ + Cu?

    <p>1.10 V</p> Signup and view all the answers

    For the reaction Cl2(g) + 2Br–(aq) → 2Cl–(aq) + Br2(l), what is the standard emf when [Cl–] = [Br–] = 0.01 M and Cl2 is at 0.25 atm?

    <p>0.272 V</p> Signup and view all the answers

    Which metal can be displaced by Zn in aqueous solutions?

    <p>Ag</p> Signup and view all the answers

    In the reaction Zn + Pb2+ → Zn2+ + Pb, what is being oxidized?

    <p>Zn</p> Signup and view all the answers

    Which gas is produced when metallic Zn reacts with acid?

    <p>H2</p> Signup and view all the answers

    In an electrochemical cell, which reaction represents reduction?

    <p>Cu2+ + 2e– → Cu</p> Signup and view all the answers

    What is the standard electrode potential, E°, for the reaction Cu+ + e– ® Cu?

    <p>0.38 V</p> Signup and view all the answers

    What are the equivalent conductances at infinite dilution for Al3+ and SO2–4 combined?

    <p>L° Al3+ + L° SO2–4</p> Signup and view all the answers

    How does the sum L° Al3+ + L° SO2–4 relate to equivalent conductance?

    <p>It gives the overall limiting conductivity of a mixture of ions.</p> Signup and view all the answers

    Which one of the following electrode potentials is NOT provided in the options?

    <p>0.55 V</p> Signup and view all the answers

    The equivalent conductance of Al3+ ion will logically be highest at what condition?

    <p>Low concentration solutions</p> Signup and view all the answers

    What is the limiting value for the combined equivalent conductance of the two ions L° Al3+ + L° SO2–4 if provided in sufficient data?

    <p>All conductances summed.</p> Signup and view all the answers

    In a context where E° values are relevant, which of the following conditions might affect the values given?

    <p>All of the above.</p> Signup and view all the answers

    The equivalent conductance of an ion is generally dependent on what main factor?

    <p>The valence and mobility of the ion.</p> Signup and view all the answers

    What is the standard cell potential using the limiting molar conductivities of NH4OH, NH4Cl, and HCl?

    <p>1.34 V</p> Signup and view all the answers

    What is the limiting molar conductivity of HCl at infinite dilution?

    <p>425.9 S cm²/mol</p> Signup and view all the answers

    How much electricity is required to completely oxidize 0.1 mol of MnO4- to MnO4?

    <p>2 × 96500 C</p> Signup and view all the answers

    Which half-reaction corresponds to the reduction of zinc ions?

    <p>Zn2+(aq) + 2e– → Zn(s)</p> Signup and view all the answers

    What is the limiting molar conductivity of NH4OH?

    <p>0.036 S cm²/mol</p> Signup and view all the answers

    What is the value of the standard reduction potential for the half-reaction involving Ag2O?

    <p>0.34 V</p> Signup and view all the answers

    Which combination of limiting molar conductivities results in the reduction of NaOH?

    <p>Lm(NH4Cl) + Lm(NaCl) - Lm(NaOH)</p> Signup and view all the answers

    What is the overall reaction that leads to the formation of silver from silver oxide?

    <p>Ag2O(s) + H2O(l) + 2e– → 2Ag(s) + 2OH–(aq)</p> Signup and view all the answers

    Study Notes

    Electrochemistry

    • Cu(s) will react with a solution containing AgNO3(aq) resulting in a blue solution. This is because Cu is more reactive than silver and will displace silver ions from the solution, forming Cu2+(aq) ions which have a blue color.
    • Zn(NO3)2(aq), Mg(NO3)2(aq), and KNO3(aq) will not react with Cu(s) and therefore will not turn blue. These metals are less reactive than copper and will not displace copper ions from solution.

    Nernst Equation

    • The Nernst Equation relates the cell potential (E) of an electrochemical cell to the standard cell potential (E°), the temperature (T), and the concentrations of the reactants and products.
    • For the reaction: Cl2(g) + 2Br–(aq) → 2Cl–(aq) + Br2(l)
    • E° = 0.29 V
    • [Cl–] = [Br–] = 0.01 M
    • P(Cl2) = 0.25 atm
    • The cell potential can be calculated using the Nernst equation: E = E° – (RT/nF)lnQ
    • E = 0.29 V – (8.314 J/mol·K × 298 K / (2 × 96485 C/mol) × ln(0.01² / 0.25))
    • E = 0.272 V

    Electrochemical Cells

    • Standard cell potential (E°) for the reaction Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) is 1.10 V at 25°C.
    • The standard cell potential represents the difference in potential between the two half-cells under standard conditions (1 atm pressure, 298 K, and 1 M concentration).
    • The positive value of E° indicates that the reaction is spontaneous under standard conditions.

    Electrolysis

    • The process of electrolysis involves using an external electric current to drive a non-spontaneous chemical reaction.
    • In the electrolysis of a solution containing Al3+(aq) and SO2–4(aq), H2(g) is liberated at the cathode and Cl2(g) is liberated at the anode.
    • This indicates that the reduction of H+ ions to H2(g) occurs at the cathode, while the oxidation of Cl– ions to Cl2(g) occurs at the anode.

    Molar Conductivity

    • Molar conductivity (Λm) is a measure of the conductivity of an electrolyte solution per unit concentration.
    • The limiting molar conductivity (Λo) refers to the molar conductivity at infinite dilution.
    • Limiting molar conductivity can be determined using the Kohlrausch's Law, which states that the limiting molar conductivity of a strong electrolyte is the sum of the limiting molar conductivities of its individual ions.

    Thermodynamic Efficiency

    • The thermodynamic efficiency of a cell is the ratio of the Gibbs Free Energy change (ΔG) to the maximum electrical work (Wmax) that can be obtained from the cell.
    • ΔG = -nFE°
    • where n is the number of moles of electrons transferred, F is the Faraday constant, and E° is the standard cell potential.
    • Wmax = -ΔG

    Electrochemical Series

    • The electrochemical series is a list of elements arranged in order of their standard reduction potentials.
    • The reducing power of a metal is directly related to its ability to lose electrons.
    • Metals higher in the electrochemical series have a greater tendency to lose electrons and are therefore stronger reducing agents.
    • The correct decreasing order of reducing power of the metals is: K > Al > Cr > Ag

    Electrolysis Calculations

    • The quantity of electricity required to completely oxidize a certain amount of a substance can be calculated using Faraday's Law of Electrolysis.
    • Faraday's constant (F) is the charge carried by one mole of electrons, which is 96485 C/mol.
    • To oxidize 0.1 mol of MnO42– to MnO4–, one mole of electrons needs to be transferred per mole of MnO42–.
    • Therefore, the quantity of electricity required is 0.1 mol × 96485 C/mol = 9648.5 C.

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    Description

    This quiz explores the principles of electrochemistry, focusing on the reaction between copper and silver ions, and the use of the Nernst Equation to calculate cell potentials. Test your understanding of the reactivity of metals and the relationship between cell potential and concentration. Perfect for students in chemistry courses.

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