Batteries and Their Functions
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Questions and Answers

What is a battery?

A device that can store chemical energy and later release it as electrical energy at a constant voltage.

What are the three main types of batteries?

  • Primary Batteries
  • Secondary Batteries
  • Flow Batteries and Fuel Cells
  • All of the above (correct)

    • Primary cells can be recharged.

    False

    What determines the lifetime of a primary cell?

    <p>The amounts of reactants present.</p> Signup and view all the answers

    The battery "dies" when the reactants have been converted into products.

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

    The voltage output of a battery remains constant throughout its lifetime.

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

    What is a secondary cell?

    <p>A secondary cell is one that can be recharged.</p> Signup and view all the answers

    To make a rechargeable battery, we must be able to reverse the redox reaction.

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

    The cell reaction must be endothermic to supply energy.

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

    An external energy source is always needed to recharge a battery.

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

    A given reaction can always be reversed.

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

    What is the defining characteristic of primary batteries?

    <p>The electrochemical reactions are not reversible.</p> Signup and view all the answers

    What is the defining characteristic of secondary batteries?

    <p>The cell reactions can be reversed.</p> Signup and view all the answers

    What is the defining characteristic of flow batteries and fuel cells?

    <p>The materials flow through the battery.</p> Signup and view all the answers

    What is the purpose of the anode in a battery?

    <p>The anode is where materials spontaneously undergo oxidation.</p> Signup and view all the answers

    What is the purpose of the electrolyte in a battery?

    <p>The electrolyte helps in the migration of ions, leading to the production of electrical current.</p> Signup and view all the answers

    What is the purpose of the separator in a battery?

    <p>The separator is a thin porous membrane that prevents the mixing of products formed at the electrodes.</p> Signup and view all the answers

    What is voltage/EMF?

    <p>Potential Difference Between two individual electrodes.</p> Signup and view all the answers

    What is current?

    <p>Rate of discharge reactions in the cell.</p> Signup and view all the answers

    What is current capacity?

    <p>The amount of current generated per unit time.</p> Signup and view all the answers

    What is power density?

    <p>The amount of power output per weight of the cell.</p> Signup and view all the answers

    Energy efficiency is applicable for both primary and secondary cells.

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

    What is cycle life?

    <p>The number of times the charging and discharging process can be repeated.</p> Signup and view all the answers

    What is self-discharge?

    <p>The battery undergoes discharging reactions even when not in operation due to the loss of active materials.</p> Signup and view all the answers

    Which of the following are differences between primary and secondary batteries?

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

    What happens during discharging in a battery?

    <p>Chemical reactions occur in the electrodes, generating a flow of current through the circuit.</p> Signup and view all the answers

    What is the most common type of secondary battery in use today?

    <p>The lead-acid battery.</p> Signup and view all the answers

    The lead-acid battery was invented in the late 19th century.

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

    What are the three main components of a single lead-acid cell?

    <p>A lead anode, a lead dioxide cathode, and a sulfuric acid electrolyte.</p> Signup and view all the answers

    Why is an insulating separator used in a lead-acid battery?

    <p>To prevent short circuiting between the anode and cathode.</p> Signup and view all the answers

    A single lead-acid cell produces a potential of approximately 12.6V.

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

    How is a 12.6V lead-acid battery typically constructed?

    <p>It is constructed of six single cells in series.</p> Signup and view all the answers

    The lead-acid battery is the first rechargeable battery ever discovered.

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

    What is the electrolyte in a lead-acid battery?

    <p>Sulfuric acid.</p> Signup and view all the answers

    Lead-acid batteries are generally categorized as nontoxic waste.

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

    What is the anode reaction in a lead-acid battery?

    <p>Pb(s) + HSO4(aq) → PbSO4(s) + H+(aq) + 2 e-</p> Signup and view all the answers

    What is the overall chemical reaction in a lead-acid battery during discharging?

    <p>Pb(s) + PbO2(s) + 2 H2SO4(aq) → 2 PbSO4(s) + 2 H2O(l)</p> Signup and view all the answers

    What happens to the concentration of H2SO4 during discharging?

    <p>It falls with discharging.</p> Signup and view all the answers

    The lead-acid battery can be recharged indefinitely.

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

    What is the anode reaction in a lead-acid battery during charging?

    <p>PbSO4(s) + H+(aq) + 2e- → Pb(s) + HSO4(aq)</p> Signup and view all the answers

    What is the most common application of lead-acid batteries?

    <p>Automobiles, for starting and lighting.</p> Signup and view all the answers

    What is a lithium-ion battery?

    <p>A rechargeable battery that is commonly used in various applications, from laptops to electric cars.</p> Signup and view all the answers

    What is the anode material in a lithium-ion battery?

    <p>A mixture of graphitic carbon and lithium.</p> Signup and view all the answers

    Lithium-ion batteries use an aqueous electrolyte.

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

    Why is lithium-ion battery technology known for its lightweight and high energy density features?

    <p>The materials used in lithium-ion batteries, such as graphite and transition metal oxides, allow for high energy storage per unit weight.</p> Signup and view all the answers

    Lithium-ion batteries are considered nontoxic waste.

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

    Overcharging lithium-ion batteries can cause a loss in efficiency.

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

    Dendrites are a potential safety concern in lithium-ion batteries.

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

    Study Notes

    Batteries

    • Batteries are devices that store chemical energy and release it as electrical energy at a constant voltage.
    • Redox reactions, involving electron transfer between species, are fundamental to battery function. Electrons move in generating and delivering electricity, connecting redox reactions to electrical systems.
    • If the oxidation and reduction half-reactions are separated, electrons can flow, creating a circuit.
    • A galvanic cell generates an electric current. A battery is a commercially significant example of a galvanic cell.

    Battery Classification

    • Primary Batteries: Electrochemical reactions are irreversible. Once the reactants are used up, no more current can be produced.
    • Secondary Batteries: Electrochemical reactions are reversible. These can be recharged and used repeatedly.
    • Flow Batteries and Fuel Cells: Materials (reactants, products, electrolyte) flow through the battery. Unlike traditional batteries, these don't store electrical energy but directly convert chemical energy into electrical at need.

    Primary Cell Structure and Lifetimes

    • The lifetime of a primary battery depends on the amount of reactants.
    • A battery "dies" when the reactants run out, halting the reaction.
    • In practice, the voltage output of a typical primary battery decreases near the end of its life, usually failing before reactants are completely consumed.

    Secondary Cell

    • Secondary cells can be recharged, offering a much longer life cycle.
    • To be rechargeable, the redox reaction must be fully reversible, converting products back to reactants. The reverse reaction needs an external energy source, like a charger, to overcome this.

    Principal Components

    • Anode: Electrode where materials oxidize, releasing electrons.
    • Cathode: Electrode where materials reduce, accepting electrons.
    • Electrolyte: Facilitates ion migration, leading to electrical current production.
    • Separator: Prevents product mixing at the electrodes and ensures only ions move through the electrolyte while electrons travel through the circuit.

    Battery Characteristics

    • Voltage/EMF: Potential difference between battery electrodes.
    • Current: Rate of discharge reactions in the cell.
    • Current Capacity: Amount of current generated per unit time.
    • Power Density: Amount of power output per unit weight of the cell.
    • Energy Density: Amount of energy available per unit weight of the cell.
    • Energy Efficiency (applicable for secondary cells): Efficiency of converting input energy to electrical output.
    • Cycle Life: Repeated number of discharge/charge cycles a battery can handle.
    • Shelf Life: Time duration a battery can store charge without use under steady conditions.
    • Self-Discharge: Battery loses charge even when not in use due to ongoing chemical reactions.

    Lead-Acid Battery

    • The lead-acid battery is one of the first commercially available secondary batteries.
    • It consists of a lead anode, lead dioxide cathode, and a sulfuric acid electrolyte.
    • A single cell produces about 2.05 volts; commonly 6 cells are connected in series to reach roughly 12.1 volts.

    Lead-Acid Battery: Discharging and Charging Process

    • Discharging involves oxidation at the anode and reduction at the cathode; electrons flow through an external circuit.
    • Lead sulfate precipitates on the electrodes.
    • Concentration of H2SO4 in the electrolyte decreases during discharging.
    • Charging reverses this process. The PbSO4 coating returns to Pb and PbO2, requiring an external energy source (like charging). The H2SO4 concentration increases in the process.

    Lead-Acid Battery: Issues

    • Overcharging: water electrolysis, hydrogen and oxygen gas generation, increased water loss, and more acid concentration lead to higher electrode corrosion.
    • Water evaporation: Increased H2SO4 concentration, increasing electrolyte viscosity, decreasing ionic mobility, requiring water re-addition
    • Leaking: New batteries need to have appropriate sealed components and housings; old batteries need proper disposal

    Lithium-ion Batteries

    • The lithium-ion battery is a popular rechargeable battery, used in laptops, cell phones and electric vehicles.
    • It's constructed with an anode (e.g., graphite) and a cathode (e.g., lithium metal oxide, often cobalt oxide).
    • An organic solvent based electrolyte is necessary to prevent oxidation. Porous separators facilitate ion flow.
    • In discharge, lithium ions move from the anode to the cathode; in charging, lithium moves back to anode.
    • Lithium-ion batteries have high energy density, making them useful in lightweight devices but are vulnerable to overcharging leading to dendrite formation, which can cause fires.

    Lithium-ion Battery Applications

    • Extensively used in consumer electronics.
    • Used in many portable electronic devices to improve power.

    Summary of Key Differences

    Feature Primary Battery Secondary Battery
    Chemical Reactions Irreversible Reversible
    Rechargeability No Yes
    Use Reusable once reacted, single use Reusable and rechargable

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    Batteries PDF

    Description

    Explore the fascinating world of batteries and how they operate. This quiz covers the fundamental principles of batteries, including redox reactions, types of batteries such as primary and secondary batteries, as well as flow batteries and fuel cells. Test your knowledge on how these energy storage devices function and their significance in electrical systems.

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