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What is produced at the anode during the electrolysis of an aqueous solution of copper sulfate?

  • Hydrogen gas
  • Cu2+ ions (correct)
  • Copper metal
  • Copper oxide

    • What is the significance of using an external voltage source in an electrolytic cell?

  • It prevents any reaction from occurring.
  • It initiates a chemical reaction by providing energy. (correct)
  • It stabilizes the solution temperature.
  • It decreases the conductivity of the electrolyte.

    • In the electrolysis of fused chlorides, which metals are typically produced?

  • Sodium and magnesium (correct)
  • Hydrogen and oxygen
  • Copper and aluminum
  • Lead and zinc

    • What happens to copper ions at the cathode during electrolysis in a copper sulfate solution?

    <p>They are reduced and deposit as copper metal.</p> Signup and view all the answers

    What is represented by the symbol $l_0$ in the context of conductivity?

    <p>Limiting molar conductivity of ions</p> Signup and view all the answers

    How can the degree of dissociation of methanoic acid be calculated using its molar conductivity?

    <p>By using the limiting molar conductivities of the ions</p> Signup and view all the answers

    Which of the following metals is produced by electrolysis of aluminum oxide in the presence of cryolite?

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

    What is the primary chemical reaction occurring at the cathode during the electrolysis of copper sulfate?

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

    What does the notation Cu(s)|Cu2+(aq)||Ag+(aq)|Ag(s) represent?

    <p>The cell notation for a galvanic cell</p> Signup and view all the answers

    Why is it impossible to measure the potential of individual half-cells directly?

    <p>The potentials are defined only in relative terms</p> Signup and view all the answers

    What is assigned a potential of zero in electrochemical measurements?

    <p>Standard Hydrogen Electrode</p> Signup and view all the answers

    Which of the following statements about the Standard Hydrogen Electrode (SHE) is NOT true?

    <p>It operates under high pressure of hydrogen gas</p> Signup and view all the answers

    What is the reaction associated with the Standard Hydrogen Electrode?

    <p>H+(aq) + e– → H(g)</p> Signup and view all the answers

    In the cell representation, what does Ecell represent?

    <p>The electromotive force of the cell</p> Signup and view all the answers

    What keeps the concentration of both forms of hydrogen in the SHE at unity?

    <p>Bubbling in pure hydrogen gas</p> Signup and view all the answers

    What role does the platinum electrode perform in the Standard Hydrogen Electrode?

    <p>It serves as a catalyst for the reaction</p> Signup and view all the answers

    What is the primary function of inexpensive conductivity meters?

    <p>To directly read the conductance or resistance of the solution</p> Signup and view all the answers

    How is molar conductivity (Lm) defined in relation to conductivity (κ)?

    <p>Lm = κ / c</p> Signup and view all the answers

    What are the units of molar conductivity (Lm) when conductivity (κ) is expressed in S m–1 and concentration (c) in mol m–3?

    <p>S m2 mol–1</p> Signup and view all the answers

    What factor affects the conductivity of solutions of different electrolytes?

    <p>The charge and size of the ions</p> Signup and view all the answers

    When conductivity (κ) is expressed in S cm–1 and concentration (c) in mol cm–3, what will be the units for molar conductivity (Lm)?

    <p>S cm2 mol–1</p> Signup and view all the answers

    What is indicated by the cell constant in the relation Lm = κ / c?

    <p>It is a proportionality constant for the setup</p> Signup and view all the answers

    What kind of electrolytes have the greatest impact on conductivity in a solution?

    <p>Strong electrolytes that completely dissociate</p> Signup and view all the answers

    In the equation for molar conductivity, what does the variable 'c' represent?

    <p>Concentration of ions in mol m–3</p> Signup and view all the answers

    Which of the following half-reactions represents the strongest oxidizing agent at 298 K?

    <p>F2(g) + 2e– → 2F–</p> Signup and view all the answers

    What is the standard electrode potential for the half-reaction involving Cu and Cu2+?

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

    Which of the following species can act as a strong reducing agent?

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

    Which half-reaction has the lowest standard electrode potential?

    <p>K+ + e– → K(s)</p> Signup and view all the answers

    At 298 K, which reaction represents the reduction of chlorine gas?

    <p>Cl2(g) + 2e– → 2Cl–</p> Signup and view all the answers

    Which of the following half-reactions involves the transfer of two electrons?

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

    What is the standard electrode potential for the half-reaction that reduces MnO4– to Mn2+?

    <p>1.51 V</p> Signup and view all the answers

    Which of the following reactions occurs with a standard electrode potential less than 0 V?

    <p>Ni2+ + 2e– → Ni(s)</p> Signup and view all the answers

    What does a higher standard electrode potential indicate regarding a species?

    <p>It is a stronger oxidizing agent.</p> Signup and view all the answers

    Which of the following metals can be best reduced among those listed?

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

    In the reaction 2H2O + 2e– → H2(g) + 2OH–, what is happening to the electrons?

    <p>Electrons are gained by H2O.</p> Signup and view all the answers

    Which half-reaction involves the change of lead ions to lead solid?

    <p>Pb2+ + 2e– → Pb(s)</p> Signup and view all the answers

    What is common about the reactions listed with potentials less than 0 V?

    <p>They require energy to occur.</p> Signup and view all the answers

    Which half-reaction would be favored in a galvanic cell due to its positive potential?

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

    What is the charge on one mole of electrons?

    <p>96487 C mol–1</p> Signup and view all the answers

    How many moles of electrons are required to deposit one mole of Mg?

    <p>2 mol</p> Signup and view all the answers

    If a current of 1.5 A is applied for 10 minutes, how much charge is passed in coulombs?

    <p>900 C</p> Signup and view all the answers

    What quantity of copper is deposited if 900 C is passed through a solution of CuSO4?

    <p>0.2938 g</p> Signup and view all the answers

    Which symbol represents the quantity of electricity equal to one mole of electrons?

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

    What determines the products of electrolysis?

    <p>Type of electrodes and electrolyte composition</p> Signup and view all the answers

    What happens when inert electrodes are used in electrolysis?

    <p>They do not participate in the reaction</p> Signup and view all the answers

    How is charge measured during electrolysis?

    <p>Current multiplied by time</p> Signup and view all the answers

    Study Notes

    Conductivity and Molar Conductivity

    • Inexpensive conductivity meters measure conductance or resistance in solutions.
    • Solution conductivity (\kappa) is calculated using the equation:
      (\kappa = G^* / R) where (G^*) is the cell constant and (R) is the resistance.
    • Conductivity varies among electrolytes due to ion charge, size, concentration, and mobility.
    • Molar conductivity (L_m) is defined as:
      (L_m = \kappa / c) where (\kappa) is conductivity and (c) is concentration.
    • Units of (L_m) vary with expression:
      • Using (S , m^{-1}) and (mol , m^{-3}), (L_m) is (S , m^2 , mol^{-1}).
      • Converting to (S , cm^{-1}) and (mol , cm^{-3}) yields (L_m) in (S , cm^2 , mol^{-1}).

    Electrode Potential Measurement

    • Electrode potentials are differential and cannot be measured directly.
    • The standard hydrogen electrode (SHE) is assigned a potential of 0 V at standard conditions.
    • SHE consists of platinum in contact with an acidic solution, with hydrogen gas bubbled through it.
    • Standard conditions for SHE include a hydrogen gas pressure of 1 bar and a 1 M concentration of (H^+).

    Standard Electrode Potentials

    • A table of standard electrode potentials at 298 K lists reactions and their voltage:
      • Strong oxidizing agents have high positive potentials (e.g., (F_2(g) + 2e^- \rightarrow 2F^- (E^\circ = 2.87 V))).
      • Strong reducing agents have lower negative potentials (e.g., (Li + e^- \rightarrow Li(s) (E^\circ = -3.05 V))).

    Electrolytic Cells and Electrolysis

    • Electrolytic cells use an external voltage source to drive chemical reactions.
    • Basic electrolytic cell example: two copper strips in copper sulfate solution.
    • At the cathode, (Cu^{2+} + 2e^- \rightarrow Cu(s)); copper deposits here.
    • At the anode, (Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-); copper oxidizes and dissolves.

    Faraday’s Laws of Electrolysis

    • Michael Faraday introduced quantitative aspects of electrolysis.
    • The charge on one mole of electrons (Faraday's constant) is (96487 , C , mol^{-1}).
    • Reactions involve specific stoichiometries for different metals:
      • (Mg^{2+} + 2e^- \rightarrow Mg(s)) requires 2 F.
      • (Al^{3+} + 3e^- \rightarrow Al(s)) requires 3 F.

    Electrolysis Products

    • Electrolysis products depend on the materials and electrode types used.
    • Inert electrodes (e.g., platinum) do not participate in reactions; reactive electrodes do.
    • Products vary based on oxidizing and reducing agents and their standard potentials.

    Practical Application Example

    • Example calculation: electrolyzing (CuSO_4) for 10 minutes with 1.5 A current.
    • The total charge calculated as: charge = current x time = (1.5 , A \times 600 , s = 900 , C).
    • Mass of copper deposited:
      [\text{mass} = \frac{63 , g , mol^{-1} \times 900 , C}{2 \times 96487 , C , mol^{-1}} = 0.2938 , g].

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