Chemistry Enthalpy and Reactions Quiz
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Questions and Answers

What does a positive change in enthalpy (ΔH) indicate about a reaction?

  • The reactants have more energy than the products.
  • Energy is released during the reaction.
  • Energy is absorbed during the reaction. (correct)
  • The temperature increases as products are formed.

    • In an exothermic reaction, which statement is true?

  • The change in enthalpy (ΔH) is positive.
  • The products contain more energy than the reactants.
  • Energy is released into the surroundings. (correct)
  • The reaction feels cold.

    • What is meant by activation energy in a chemical reaction?

  • The total energy released from a reaction.
  • The minimum energy required for reactants to collide successfully. (correct)
  • The energy that remains after a reaction occurs.
  • The energy absorbed by products during a reaction.

    • Which statement correctly describes the relationship between reactants and products in an endothermic reaction?

    <p>Products have higher energy than reactants.</p> Signup and view all the answers

    What is the role of a catalyst in a chemical reaction?

    <p>It lowers the activation energy barrier to increase the reaction rate.</p> Signup and view all the answers

    How does the temperature of a reaction typically change during an endothermic process?

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

    What is an activated complex in a chemical reaction?

    <p>The temporary and unstable arrangement of atoms during the reaction.</p> Signup and view all the answers

    What is the effect of a catalyst on the heat of reaction (ΔH)?

    <p>It has no effect on ΔH.</p> Signup and view all the answers

    Study Notes

    Enthalpy

    • Enthalpy (H) is the measure of heat energy.
    • Change in enthalpy (ΔH) indicates the amount of energy absorbed or released during a reaction.
    • ΔH = Hproducts – Hreactants
    • Positive ΔH: energy is absorbed (endothermic)
    • Negative ΔH: energy is released (exothermic)

    Endothermic Reaction

    • Heat (energy) is absorbed into the reaction.
    • The reaction feels cold, temperature decreases.
    • Products have higher energy than reactants.
    • ΔH is positive.

    Exothermic Reaction

    • Heat (energy) is released from the reaction.
    • The reaction feels hot, temperature increases.
    • Reactants have higher energy than products.
    • ΔH is negative.

    Collision Theory

    • Two atoms, ions, or molecules react to form products when they collide with enough energy.
    • This energy is called the activation energy.
    • It is the minimum energy required for colliding particles to react.

    Activated Complex

    • An unstable arrangement of atoms forms momentarily at the activation energy barrier.
    • Also known as the transition state.

    Catalyst

    • A catalyst increases the rate of a reaction by lowering the activation energy barrier.
    • It does not impact the heat of reaction (ΔH).

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    Related Documents

    Endothermic and Exothermic Reactions PDF

    Description

    Test your knowledge on enthalpy, endothermic and exothermic reactions, and collision theory. This quiz covers key concepts such as energy absorption and release, activation energy, and the characteristics of the activated complex. Perfect for chemistry students looking to reinforce their understanding of thermodynamics.

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