Electrolysis Concepts and Reactions
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Questions and Answers

What is the role of the anode in the electroplating process?

  • To attract cations from the electrolyte
  • To gain electrons and become negatively charged
  • To lose electrons and become positively charged (correct)
  • To provide a surface for electroplating

    • During electrolysis, the cathode is positively charged.

    False

    What charge do cations carry in the electrolysis process?

    Positive

    At the anode, silver atoms lose electrons and become __________ in the electrolyte.

    <p>silver ions</p> Signup and view all the answers

    Match the following components of electroplating with their functions:

    <p>Cathode = Site of reduction and silver deposition Anode = Source of silver ions Electrolyte = Medium for ion movement Direct current power supply = Provides electrons to the system</p> Signup and view all the answers

    What is produced at the anode when halide ions are present?

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

    In the electrolysis of brine, chlorine gas is produced at the cathode.

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

    What do Na+ and OH– ions form after electrolysis of brine?

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

    At the cathode of dilute sulfuric acid, _______ ions are attracted.

    <p>H+</p> Signup and view all the answers

    Match the following solutions with their properties:

    <p>Brine = Contains concentrated NaCl Dilute sulfuric acid = Referred to as acidified water Platinum = Inert electrode material Chlorine = Produced at the anode in brine</p> Signup and view all the answers

    Which ions are produced at the cathode when Na is more reactive than hydrogen?

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

    Oxygen and water are produced at the anode during the electrolysis of dilute sulfuric acid.

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

    What is the primary reason for using inert electrodes in dilute sulfuric acid electrolysis?

    <p>They do not react with the electrolyte.</p> Signup and view all the answers

    What is the primary process of electrolysis?

    <p>Decomposition of an ionic compound by electric current</p> Signup and view all the answers

    During electrolysis, the positive ions are attracted to the anode.

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

    Name the product formed at the cathode during the electrolysis of molten lead(II) bromide.

    <p>Lead (Pb)</p> Signup and view all the answers

    Electrolysis involves the decomposition of an __________ compound in molten or aqueous solution.

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

    Match the following components of electrolysis with their descriptions:

    <p>Anode = Positively charged electrode Cathode = Negatively charged electrode Electrolyte = Ionic compound in molten or aqueous state Direct Current = Electricity that flows in one direction</p> Signup and view all the answers

    What happens to bromide ions during the electrolysis of molten lead(II) bromide?

    <p>They lose electrons and form bromine atoms that pair up</p> Signup and view all the answers

    What is produced at the anode during the electrolysis of concentrated aqueous sodium chloride?

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

    In the electrolysis of aqueous solutions, hydrogen ions are attracted to the cathode.

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

    What is produced at the cathode during the electrolysis of molten salts?

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

    At the anode, oxygen is always produced when electrolysis occurs.

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

    What ions are produced when aluminium oxide (Al2O3) is molten?

    <p>Al3+ and O2–</p> Signup and view all the answers

    At the anode, the O2– ions will ______ electrons to form ______.

    <p>lose; oxygen gas</p> Signup and view all the answers

    Match the components of electrolysis to their roles:

    <p>Cathode = Receives positive ions and produces metal Anode = Receives negative ions and produces non-metal Electrolyte = Contains ions of the plating metal for electroplating Plating metal = Anode in an electroplating process</p> Signup and view all the answers

    What is NOT a purpose of electroplating?

    <p>Enhancing electrical conductivity</p> Signup and view all the answers

    During electrolysis, the cathode is the object that gains electrons.

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

    What kind of ions will be attracted to the anode during electrolysis?

    <p>Negative ions</p> Signup and view all the answers

    What do chloride ions form at the anode during electrolysis?

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

    Hydrogen is always produced at the anode during the electrolysis of halide compounds.

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

    Which ions are attracted to the cathode in the electrolysis of copper chloride solution?

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

    At the anode, __________ ions lose electrons and form halogens.

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

    Match the halide ion to its corresponding halogen product formed at the anode:

    <p>Cl– = Cl2 Br– = Br2 I– = I2</p> Signup and view all the answers

    What happens at the cathode if the metal ion is more reactive than hydrogen?

    <p>Hydrogen gas will be produced.</p> Signup and view all the answers

    Oxidation refers to the gain of electrons.

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

    Write the half-equation for the oxidation of chloride ions to form chlorine gas.

    <p>2Cl– -&gt; Cl2 + 2e–</p> Signup and view all the answers

    What does the mnemonic OILRIG stand for?

    <p>Oxidation Is Loss of electrons, Reduction Is Gain of electrons</p> Signup and view all the answers

    Reduction occurs at the anode.

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

    Write the half equation for the reduction of aluminium ions at the cathode.

    <p>Al 3+ + 3e – -&gt; Al</p> Signup and view all the answers

    Chlorine ions need to gain ______ electrons to form chlorine gas.

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

    Match the following ions with their respective processes:

    <p>Al 3+ = Reduction Cl – = Oxidation Cations = Gain of electrons Electrons = Negative charge</p> Signup and view all the answers

    Study Notes

    Electrolysis

    • Electrolysis is the decomposition of an ionic compound (molten or aqueous) by an electric current.

    Electrolytic cells

    • Anode: Positive electrode, attracts negatively charged ions
    • Cathode: Negative electrode, attracts positively charged ions
    • Electrolyte: Molten or aqueous ionic compound; ions are free to move.
    • Direct current (DC) supply: Connects to electrodes.

    Products of Electrolysis

    • (a) Molten Lead(II) Bromide (PbBr₂):*

    • Metal forms at the cathode; non-metal at the anode.

    • Cathode: Pb²⁺ ions gain electrons to form Pb atoms (lead).

    • Anode: Br⁻ ions lose electrons to form Br₂, which is diatomic bromine.

    • (b) Concentrated Aqueous Sodium Chloride (NaCl):*

    • At the cathode: Hydrogen ions (H⁺) gained electrons and produced hydrogen gas (H₂).

    • At the anode: Chloride ions (Cl⁻) lost electrons and formed chlorine gas (Cl₂). Sodium ions and hydroxide ions are left behind which will form sodium hydroxide.

    • (c) Dilute Sulfuric Acid (H₂SO₄):*

    • Cathode: Hydrogen ions gained electrons to form hydrogen gas (H₂).

    • Anode: Hydroxide ions lost electrons to form oxygen gas (O₂).

    Electroplating

    • Thin layer of one metal is deposited on another.
    • Purpose: improve appearance or corrosion resistance.
    • The object to be plated (cathode), the metal to be plated onto the object (anode), and an electrolyte of the metal that being plated.

    (Extended) Charge Transfer During Electrolysis

    • External circuit: Electrons flow from the power supply to the cathode and back to the anode.
    • Electrolyte: Ions move towards opposite electrodes (cations to cathode, anions to anode) through the solution carrying the charge.

    (Extended) Electrolysis of a Halide Compound

    • Anode: Halide ions lose electrons; produce respective halogen gas.
    • Cathode: H⁺ ions gain electrons (preferential reduction occurs if metal ions are present); produces hydrogen gas. If a less reactive metal is present it forms that metal instead.

    (Extended) Half Equations

    • Oxidation half equations show electron loss (anode) and reduction equations show electron gain (cathode).
    • Overall charges and numbers of atoms must be balanced.

    (Extended) Electrolysis of Aqueous Copper(II) Sulfate (CuSO₄)

    • Inert Electrodes (Carbon/Graphite):
      • Cathode: Copper ions (Cu²⁺) gain electrons from the cathode to form copper metal. This reduces the concentration of copper ions and the blue colour of the solution fades.
      • Anode: Hydroxide ions (OH⁻) lose electrons and produce oxygen gas.
    • Copper Electrodes:
      • Cathode: Copper ions (Cu²⁺) deposit on the cathode which is now a copper electrode, reducing the solution's copper concentration with copper accumulating on the cathode.
      • Anode: The anode dissolves into ions again with the copper ions entering the solution. This maintains the solution's copper concentration.

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    CAIE IGCSE Chemistry 4.1 Electrolysis PDF

    Description

    Explore the fundamental concepts of electrolysis, including electrolytic cells, electrodes, and products formed during decomposition. This quiz covers specific reactions such as those involving molten lead(II) bromide and concentrated aqueous sodium chloride. Perfect for students looking to test their understanding of electrochemical processes.

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