Electrolysis and Electroplating Overview
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Questions and Answers

What is the main function of an electrolytic cell?

  • To generate spontaneous reactions using electrical energy
  • To measure the electric potential of cells
  • To drive nonspontaneous reactions using electrical energy (correct)
  • To produce heat energy through chemical reactions

    • Which statement correctly describes a voltaic cell?

  • It produces a current through electrolysis
  • It converts chemical energy into electrical energy (correct)
  • It operates under nonspontaneous conditions
  • It requires an external power source to function

    • What occurs at the anode during electrolysis?

  • No reaction takes place
  • Reduction of cations
  • Oxidation of the substance being oxidized (correct)
  • Oxidation of anions

    • How is the quantity of products formed in electrolysis related to current?

    <p>Proportional to the current</p> Signup and view all the answers

    What happens to the electrodes when a voltaic cell is converted into an electrolytic cell?

    <p>Cathode becomes anode and vice versa</p> Signup and view all the answers

    For a reaction with a cell potential of $E°cell = -0.48 V$, what type of reaction is anticipated without an external power source?

    <p>Nonspontaneous reaction</p> Signup and view all the answers

    What is the significance of the electric potential in driving electrolysis?

    <p>It must exceed the cell potential for nonspontaneous reactions</p> Signup and view all the answers

    Which of the following is an example of an application of electrolysis?

    <p>Refining metals from their ores</p> Signup and view all the answers

    Which statement correctly describes the process at the anode in a voltaic cell?

    <p>Oxidation occurs and electrons are lost.</p> Signup and view all the answers

    What is the standard cell potential ($E°cell$) for the electrolysis of molten sodium chloride?

    <p>-4 V</p> Signup and view all the answers

    In the electrolysis of water, what is the role of H2SO4?

    <p>It provides necessary ions to carry the electric current.</p> Signup and view all the answers

    Which of the following is a product formed during the electrolysis of molten sodium chloride?

    <p>Chlorine gas</p> Signup and view all the answers

    What occurs at the cathode during the electrolysis of water?

    <p>Hydrogen ions are reduced and hydrogen gas is produced.</p> Signup and view all the answers

    What is the overall reaction for the electrolysis of water?

    <p>2 H2O (l) → 2 H2 (g) + O2 (g)</p> Signup and view all the answers

    How does the cell potential ($E°cell$) differ between an electrolysis and a voltaic cell?

    <p>Voltaic cells have a higher potential than electrolysis.</p> Signup and view all the answers

    What happens at the anode during the electrolysis of aqueous sodium chloride solution?

    <p>Chlorine gas is produced.</p> Signup and view all the answers

    What is the role of cryolite in the electrolysis of aluminum oxide?

    <p>It lowers the melting point of aluminum oxide.</p> Signup and view all the answers

    During the electrolysis of copper, what happens at the cathode?

    <p>Cu is reduced from Cu²⁺ ions.</p> Signup and view all the answers

    What is formed at the anode during the electrorefining of copper?

    <p>Cu²⁺ ions.</p> Signup and view all the answers

    In the overall reaction for aluminum electrolysis, how many aluminum atoms are produced from aluminum ions?

    <ol start="2"> <li></li> </ol> Signup and view all the answers

    Which statement is true regarding the electroplating process?

    <p>The electrolyte solution contains the metal ions for plating.</p> Signup and view all the answers

    What is the effect of electrorefining on the purity of metal?

    <p>It increases the purity of the metal.</p> Signup and view all the answers

    Which equation represents oxidation in the electrorefining process of copper?

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

    What describes the movement of ions during electrolysis in the copper refining process?

    <p>Cu²⁺ ions migrate to the cathode.</p> Signup and view all the answers

    What is the oxidation reaction that occurs at the anode during the electrolysis of aqueous sodium chloride?

    <p>2 Cl⁻ (aq) → Cl2 + 2e¯</p> Signup and view all the answers

    Which reduction reaction is preferred at the cathode when the pH is 7 in the electrolysis of NaCl solution?

    <p>2 H2O (1) + 2e → H2 (g) + 2 OH¯(aq)</p> Signup and view all the answers

    What phenomenon describes the difference between the electrode potential and the voltage required to cause electrolysis?

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

    What by-product can be obtained by evaporating the aqueous solution after electrolysis of NaCl solution?

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

    Why is reaction 5 (Na⁺ + e¯ → Na) ruled out during the electrolysis of aqueous sodium chloride?

    <p>It has a very negative standard reduction potential.</p> Signup and view all the answers

    What is the principal ore of aluminum that is utilized for its extraction?

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

    What treatment is required for solid-state ore before electrolysis to liberate metal?

    <p>Reaction with a strong acid</p> Signup and view all the answers

    What happens to the concentration of Cl⁻ ions during electrolysis of aqueous sodium chloride?

    <p>It decreases.</p> Signup and view all the answers

    What does Faraday's law of electrolysis state about the product formed at an electrode?

    <p>It is directly proportional to the amount of current flowing through the cell.</p> Signup and view all the answers

    In the balanced half-reaction for chromium plating, what is the role of e⁻?

    <p>They are gained by Cr³⁺ ions to reduce them to solid Cr.</p> Signup and view all the answers

    How is the total charge calculated in the electrolysis process?

    <p>By multiplying the moles of electrons transferred by Faraday's constant.</p> Signup and view all the answers

    What is the current required if 4.8 x 10³ C of charge is used over 12.5 minutes?

    <p>6.4 A</p> Signup and view all the answers

    What is the first step in calculating the amount of current needed for electrolysis?

    <p>Determine the balanced half-reaction for the substance.</p> Signup and view all the answers

    Why is the ratio of moles of electrons to moles of solid chromium 3:1?

    <p>Because each chromium atom requires 3 electrons to be reduced.</p> Signup and view all the answers

    What is the purpose of using Faraday's constant during electrolysis calculations?

    <p>To relate the moles of electrons to the total charge.</p> Signup and view all the answers

    What happens when the current flowing through the electrolytic cell increases?

    <p>The rate of production of product increases.</p> Signup and view all the answers

    Study Notes

    Electrolysis and Electroplating

    • Electrolysis is a process using electrical energy to drive a nonspontaneous reaction, useful in chemical production, metal refining, and corrosion prevention.
    • Electrolysis relies on an electrolytic cell.
    • The amount of product formed is directly proportional to the current flowing through the electrolytic cell.

    Learning Outcomes

    • Define electrolysis and provide an example.
    • Explain the principle of an electrolytic cell.
    • Calculate charge and product amounts in an electrolytic cell.

    Motivation Questions

    • How is aluminum produced?
    • Can a rusty spoon be made silver?
    • Can plastic be turned to gold or silver?

    Electrolytic Cell and Electrolysis

    • An electrolytic cell is the reverse of a voltaic cell--it uses external energy to drive a nonspontaneous reaction.

    Sn-Cu Voltaic Cell (Example)

    • Voltaic cell reaction: Sn(s) + Cu²⁺(aq) → Sn²⁺(aq) + Cu(s)
    • E°cell = 0.48 V, ΔG° = -93 kJ

    Reversing the Cell Reaction

    • Reversing the reaction (Sn²⁺(aq) + Cu(s) → Sn(s) + Cu²⁺(aq)) requires more energy (a nonspontaneous reaction), which converts the voltaic cell into an electrolytic cell.

    Table 1: Comparison of Voltaic and Electrolytic Cells

    • Voltaic cell: ΔG < 0, Ecell > 0, Anode (oxidation): -, Cathode (reduction): +,
    • Electrolytic cell: ΔG > 0, Ecell < 0, Anode (oxidation): +, Cathode (reduction): -

    Applications of Electrolysis

    Production of Chemicals

    • Electrolysis of Molten Sodium Chloride (NaCl):
      • Downs cell is used industrially.
      • Overall Reaction: 2Na⁺(l) + 2Cl⁻(l) → Cl₂(g) + 2Na(l)
      • Requires a minimum of 4 V to proceed.
    • Electrolysis of Water:
      • Requires an external energy source (such as a battery).
      • Overall Reaction: 2H₂O(l) → 2H₂(g) + O₂(g)

    Extraction of Metals (Aluminium)

    • Extraction of Aluminum:
      • Purified aluminum oxide (alumina) is mixed with cryolite to lower its melting point and then electrolyzed.
      • Overall Reaction (reduction): 2Al³⁺(l) + 6e⁻ → 2Al(l)  

    Refining of Metals (Copper)

    • Electrorefining of Copper:
      • Impure copper is oxidized at the anode, and pure copper is deposited at the cathode.

    Electroplating

    • Electroplating:
      • Plating a metal onto another metal (or object) using electrolysis.
      • Example: plating a spoon with silver using a silver anode.

    Stoichiometry of Electrolysis

    • Faraday's Law of Electrolysis: The amount of substance produced is directly proportional to the current.
    • Calculate the amount of substance produced or needed, given the current and time.

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    Lesson 3.4: Electrolysis and Electroplating PDF

    Description

    Explore the fascinating processes of electrolysis and electroplating through this quiz. Learn about electrolytic cells, calculate charge and product amounts, and understand how these principles apply to real-world scenarios like aluminum production and metal refinement. Test your knowledge and deepen your understanding of these essential chemical processes.

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