Balancing Redox Reactions and Voltaic Cells
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Questions and Answers

What is required to balance the half-reaction for MnO4-?

  • 2 Mn2+
  • 10 e-
  • 16 H+ (correct)
  • 8 H+
  • What happens to the electrons when the two half-reactions are combined?

  • They are ignored during balancing.
  • They add up to more than 10.
  • They cancel out completely. (correct)
  • They remain part of the final equation.
  • What is plentiful in an acidic medium that affects redox reactions?

  • H3O+ ions
  • H2O molecules and H+ ions (correct)
  • H2O and OH- ions
  • OH- ions
  • Which ions are scarce in basic medium during the balancing of redox reactions?

    <p>H3O+ ions</p> Signup and view all the answers

    What does the final balanced equation indicate about mass and charge?

    <p>Both mass and charge are balanced.</p> Signup and view all the answers

    Which of the following is true regarding balancing in a basic medium?

    <p>Water molecules and OH- ions are used.</p> Signup and view all the answers

    What is done with the H+ ions in a basic medium equation?

    <p>They are combined with an equal number of OH- ions.</p> Signup and view all the answers

    How many OH- ions need to be added to the equation if there are 16 H+ ions?

    <p>16 OH- ions</p> Signup and view all the answers

    What do H+ and OH- ions form when combined?

    <p>Water molecules</p> Signup and view all the answers

    When the reaction is balanced for a basic medium, what is expected to appear in the final balanced equation?

    <p>Water molecules and OH- ions</p> Signup and view all the answers

    In a reaction occurring in acidic medium, what is the role of H+ ions?

    <p>They react with OH- to form water.</p> Signup and view all the answers

    What happens to the water molecules in the final equation after balancing?

    <p>Some are canceled out due to being on both sides.</p> Signup and view all the answers

    Which of the following represents the correct transformation when moving from acidic to basic medium?

    <p>Add OH- ions equal to the number of H+ ions.</p> Signup and view all the answers

    What is the final balanced equation for the reaction in basic medium?

    <p>5 Cu + 2 MnO4- + 8 H2O → 5 Cu + 2 Mn + 16 OH-</p> Signup and view all the answers

    What type of reaction occurs at the anode in a voltaic cell?

    <p>Oxidation half-reaction</p> Signup and view all the answers

    Which mnemonic can help remember the relationship between anode and oxidation?

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

    Which element undergoes reduction in the half-reaction Fe3+ + H2 + OH- → Fe2+ + 2 H2O?

    <p>Iron (Fe)</p> Signup and view all the answers

    What is the meaning of OIL in the OIL RIG mnemonic?

    <p>Oxidation Involves Loss</p> Signup and view all the answers

    What occurs at the cathode in a voltaic cell?

    <p>Gain of electrons</p> Signup and view all the answers

    In the reaction 2 Al + 3 Zn2+ + 8 OH- → 2 Al(OH)4- + 3 Zn, which species is reduced?

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

    How did early chemists classify metals before the invention of the Periodic Table?

    <p>By reactivity towards water</p> Signup and view all the answers

    What does the 'R' in the OIL RIG mnemonic represent?

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

    What is formed when Cu2+ and Mn2+ combine in a basic solution?

    <p>Cu(OH)2 and Mn(OH)2</p> Signup and view all the answers

    Who discovered the concept of a battery known as the voltaic pile?

    <p>Alessandro Volta</p> Signup and view all the answers

    Which electrode receives the flow of electricity from the electrolyte in a voltaic cell?

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

    What substance was used to connect the dissimilar metals in Volta's battery?

    <p>Cardboard soaked in brine</p> Signup and view all the answers

    Which term did Michael Faraday introduce to describe the metals in a battery?

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

    What misconception did early scientists have about electricity?

    <p>It is a fluid that flows from one object to another.</p> Signup and view all the answers

    What ions precipitate in the reaction involving Cu2+ and MnO4- in basic conditions?

    <p>Cu(OH)2 and Mn(OH)2</p> Signup and view all the answers

    Which solution type causes MnO4- to convert to Mn2+ in a redox reaction?

    <p>Acidic solution</p> Signup and view all the answers

    What is the first step in balancing half-reactions?

    <p>Identify the element undergoing a change in oxidation state.</p> Signup and view all the answers

    How do you balance oxygen atoms in a half-reaction?

    <p>By adding H2O molecules.</p> Signup and view all the answers

    In the half-reaction Cu → Cu2+ + 2e-, how is the charge balanced?

    <p>By adding 2 electrons to the right side.</p> Signup and view all the answers

    Which step involves balancing hydrogen in a half-reaction?

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

    What must be true about the total numbers of atoms when balancing half-reactions?

    <p>They must be the same on both sides.</p> Signup and view all the answers

    How do you balance the half-reaction MnO4- + 8H+ + 5e- → Mn2+ + 4H2O?

    <p>By balancing H atoms then adding H2O.</p> Signup and view all the answers

    What charge is assigned to the left side of the half-reaction Cu → Cu2+ + 2e-?

    <p>0</p> Signup and view all the answers

    Why is it necessary to balance charges in a half-reaction?

    <p>To ensure conservation of mass and charge.</p> Signup and view all the answers

    Study Notes

    Balancing Redox Reactions

    • The ion-electron method balances redox reactions by ensuring the same number of atoms and charges on both sides of the equation.
    • The method involves dividing the reaction into half-reactions, balancing each separately, and then combining them.
    • Balancing half-reactions involves balancing elements (except hydrogen or oxygen), oxygen by adding H2O, hydrogen by adding H+, and charges by adding electrons.
    • In basic medium, after combining balanced half-reactions, OH- ions are added to both sides of the equation to neutralize H+ ions.

    Voltaic Cell

    • Voltaic cells use redox reactions to generate electricity.
    • Two dissimilar metals, called electrodes, are connected by an electrolyte (a solution that conducts electricity).
    • The electrode where oxidation occurs is called the anode, and the electrode where reduction occurs is called the cathode.
    • The anode loses electrons, while the cathode gains electrons.
    • Mnemonic: Anode-Oxidation (both begin with vowels), Cathode-Reduction (both begin with consonants).
    • OIL RIG: Oxidation-Loss of Electrons, Reduction-Gain of Electrons.

    Activity Series and Electromotive Force

    • The activity series classifies metals based on their reactivity with water.
    • The electromotive force (EMF) is the potential difference (voltage) between two electrodes in a voltaic cell.
    • The EMF depends on the specific metals used and the concentration of the electrolyte.
    • Higher EMF indicates a greater tendency for the redox reaction to occur.

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    Description

    This quiz explores the balancing of redox reactions using the ion-electron method and the functioning of voltaic cells. You'll learn how to balance half-reactions and understand the roles of anodes and cathodes in electricity generation. Test your knowledge of these fundamental concepts in electrochemistry!

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