General Chemistry 2: Enthalpy of a Reaction
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Questions and Answers

What is the correct definition of internal energy of a system?

  • It is the difference of the kinetic energy and potential energy of all its components.
  • It is the sum of the kinetic energy and potential energy of all its components. (correct)
  • It is the sum of the heat energy and solar energy of all its components.
  • It is the product of the kinetic energy and potential energy of all its components.

    • Which of the following quantities is NOT involved in enthalpy?

  • Pressure (correct)
  • Internal Energy
  • Heat
  • Volume

    • What is the best description of enthalpy?

  • A thermodynamic quantity that measures the flow of energy in a chemical reaction.
  • A thermodynamic quantity that measures the chemical changes in a chemical reaction.
  • A thermodynamic quantity that measures the acquired energy in a chemical reaction.
  • A thermodynamic quantity that measures the energy changes in a chemical reaction. (correct)

    • Which of the following pairs of descriptions differentiates endothermic and exothermic reactions?

    <p>Endothermic : absorbs energy ; Exothermic : releases energy</p> Signup and view all the answers

    What is the primary difference between internal energy and enthalpy?

    <p>Internal energy is a path function, while enthalpy is a state function.</p> Signup and view all the answers

    Which of the following statements about energy transformations is TRUE?

    <p>Energy can be transformed from one form to another in a chemical reaction.</p> Signup and view all the answers

    What is the definition of enthalpy in a system?

    <p>The sum of its internal energy plus the product of its pressure and volume</p> Signup and view all the answers

    What type of function is enthalpy?

    <p>A state function</p> Signup and view all the answers

    What happens to the enthalpy of a system when heat flows from the system to its surroundings?

    <p>The enthalpy of the system decreases</p> Signup and view all the answers

    What is the purpose of using enthalpy in chemical reactions?

    <p>To measure the energy changes that occur in the reaction</p> Signup and view all the answers

    What is the change in enthalpy represented by?

    <p>ΔH = Hfinal - Hinitial</p> Signup and view all the answers

    What is the type of reaction when the enthalpy of a reaction is positive?

    <p>Endothermic reaction</p> Signup and view all the answers

    What is the enthalpy change that accompanies the melting of 1 mol of a substance?

    <p>Enthalpy of fusion</p> Signup and view all the answers

    What is the internal energy of a system?

    <p>The sum of the kinetic energy and potential energy of all its components</p> Signup and view all the answers

    Which of the following is a state function?

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

    What is the correct definition of a change in enthalpy?

    <p>ΔH = Hfinal – Hinitial</p> Signup and view all the answers

    What is the main difference between enthalpy and enthalpy of a reaction?

    <p>Enthalpy is the change in energy that happens in a chemical reaction, while enthalpy of a reaction is the difference in enthalpy between products and reactants</p> Signup and view all the answers

    What is the relation between enthalpy and internal energy?

    <p>Enthalpy is the sum of internal energy and pressure</p> Signup and view all the answers

    Study Notes

    Understanding Enthalpy

    • Enthalpy is a thermodynamic quantity used to measure energy changes in chemical reactions.
    • It is defined as the sum of internal energy (U) and the product of pressure (P) and volume (V): H = U + PV.
    • Enthalpy is a state function, meaning it only depends on the current state of a system and not on how it got there.

    Internal Energy vs. Enthalpy

    • Internal energy is the sum of kinetic energy (KE) and potential energy (PE) of all components in a system.
    • Internal energy is related to enthalpy, but they are not the same thing.

    Measuring Enthalpy Changes

    • Enthalpy changes (ΔH) are measured in chemical reactions, and can be positive or negative.
    • A negative enthalpy change indicates an exothermic reaction, where heat flows from the system to the surroundings.
    • A positive enthalpy change indicates an endothermic reaction, where heat flows from the surroundings to the system.

    Types of Enthalpy Changes

    • The enthalpy change that accompanies the melting (fusion) of 1 mol of a substance is a specific type of enthalpy change.
    • The enthalpy change that accompanies the vaporization of 1 mol of a substance is another specific type of enthalpy change.

    Key Concepts

    • Enthalpy is a state function, and changes in enthalpy can be measured in chemical reactions.
    • Enthalpy is not the same as internal energy, but they are related.
    • Enthalpy changes can be positive or negative, indicating endothermic or exothermic reactions.

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    Description

    Test your knowledge on enthalpy in the context of chemical reactions. This quiz is designed for Grade 12 learners and covers the basics of enthalpy in General Chemistry 2.

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