Photochemical Reaction in Chemistry
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Questions and Answers

Secondary processes occur in the presence of light.

False

What is the primary process in photochemical reactions?

  • Activation of molecules
  • Formation of products
  • Absorption of light (correct)
  • Decomposition of reactants

    • What is the law of photochemical equivalence?

    One molecule reacts with one quantum of light.

    The primary process involves the absorption of light, leading to the ______________ of molecules.

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

    What is the result of photochemical reactions?

    <p>Yield of products</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Primary process = Absorption of light by reactant molecules Secondary process = Reactions that occur in the absence of light Quantum yield = Number of molecules reacting per quantum of light Photochemical reaction = Reaction involving light</p> Signup and view all the answers

    The quantum yield of a reaction is always greater than one.

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

    What is the role of light in photochemical reactions?

    <p>To activate reactant molecules.</p> Signup and view all the answers

    What is the primary process in the photochemical reaction described in the passage?

    <p>Chain initiating step</p> Signup and view all the answers

    The chain propagation steps in the photochemical reaction have relatively high activation energies.

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

    What is the name of the step that produces a large number of HCI molecules before the chain is terminated?

    <p>Chain propagation step</p> Signup and view all the answers

    The chain is finally terminated by the combination of chlorine radicals on the walls of the vessel or in gas _____________.

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

    What is the result of the chain propagation steps in the photochemical reaction?

    <p>A large number of HCI molecules are produced</p> Signup and view all the answers

    The chain terminating step is exothermic.

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

    Match the following steps with their descriptions:

    <p>Chain initiating step = This is followed by the secondary processes Chain propagating step = Producing a large number of HCI molecules before the chain is terminated Chain terminating step = Combination of chlorine radicals on the walls of the vessel or in gas phase</p> Signup and view all the answers

    What is the primary process in photochemical reactions?

    <p>Activation of molecules</p> Signup and view all the answers

    The law of photochemical equivalence states that one molecule of reactant is activated per quantum of light absorbed.

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

    What is the significance of the ratio 1:1 in photochemical reactions?

    <p>This ratio indicates that one molecule is activated per quantum of light absorbed.</p> Signup and view all the answers

    The energy from light is absorbed by molecules at wavelengths around _________ Å.

    <p>4800</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Primary Process = Breaking of chemical bonds Secondary Process = Activation of molecules Law of Photochemical = One molecule of reactant is activated per quantum of light absorbed Photochemical Reaction = Chain reaction involving multiple molecules</p> Signup and view all the answers

    What is the effect of increasing the number of quanta on the rate of photochemical reactions?

    <p>The rate of reaction increases</p> Signup and view all the answers

    In photochemical reactions, the energy from light is directly used to break chemical bonds.

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

    What is the role of Nernst in the development of photochemistry?

    <p>Nernst proposed the law of photochemical equivalence in 1918.</p> Signup and view all the answers

    Study Notes

    Photochemical Reaction

    • Photochemical reaction is a primary process that forms hydrogen and other molecules through the absorption of light
    • This process was discovered by Nernst in 1918
    • It involves the absorption of quanta, which are packets of energy, and this leads to the formation of new molecules

    Chain Reaction

    • A chain reaction is a process that involves the formation of new molecules through a series of reactions
    • It involves the absorption of quanta, which leads to the formation of activated molecules
    • These activated molecules then react with other molecules to form new molecules, and this process continues until it is terminated
    • The chain reaction is characterized by a high yield of products and a low activation energy

    Initiating Step

    • The initiating step is the first step in a chain reaction
    • It involves the absorption of a photon by a molecule, leading to its activation
    • The activated molecule then reacts with another molecule to form a new molecule

    Propagating Steps

    • The propagating steps are the reactions that follow the initiating step
    • They involve the reaction of activated molecules with other molecules to form new molecules
    • These steps are exothermic and have low activation energies, which means they occur rapidly and repeatedly

    Terminating Step

    • The terminating step is the final step in a chain reaction
    • It involves the combination of two radicals to form a stable molecule
    • This step stops the chain reaction from continuing

    Characteristics of Chain Reactions

    • Chain reactions are characterized by a high yield of products
    • They involve the absorption of quanta, which leads to the formation of activated molecules
    • They have low activation energies, which means they occur rapidly
    • They can produce a large number of molecules before being terminated

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    Description

    This quiz covers the primary products formed under photochemical reaction in chemistry. Test your knowledge of chemical reactions and processes.

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