Chemistry Chapter 5 Quiz
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Questions and Answers

Which statement describes an exothermic reaction?

  • The enthalpy change is positive.
  • It releases energy to the surroundings. (correct)
  • The products have a higher energy content than the reactants.
  • It absorbs heat from the surroundings.
  • What is the correct sign of the enthalpy change (∆H) for an endothermic reaction?

  • ∆H > 0 (correct)
  • ∆H = 0
  • ∆H < 0
  • ∆H = -1
  • Which process would be classified as an endothermic reaction?

  • Combustion of methane
  • Thermal decomposition of calcium carbonate (correct)
  • Dissolving anhydrous salts
  • Neutralization of an acid
  • What is the relationship between the energy content of reactants and products in an exothermic reaction?

    <p>Reactants have higher energy than products. (A)</p> Signup and view all the answers

    Identify the reaction type that is more energetically favorable.

    <p>Exothermic reactions (A)</p> Signup and view all the answers

    In a reaction pathway diagram, what aspect does the vertical axis typically represent?

    <p>Energy levels of reactants and products (A)</p> Signup and view all the answers

    How does the stability of a system relate to the enthalpy change (∆H) value?

    <p>More negative ∆H values indicate more stability. (C)</p> Signup and view all the answers

    Which of the following reactions is an example of combustion?

    <p>Reaction of hydrogen gas with oxygen (C)</p> Signup and view all the answers

    Why does ozone not convert to oxygen immediately in the atmosphere?

    <p>It is kinetically stable but energetically unstable. (C)</p> Signup and view all the answers

    What is the formula to calculate heat energy absorbed or released in a reaction?

    <p>Heat energy = mc∆T (C)</p> Signup and view all the answers

    Which assumption is made when calculating enthalpy changes for aqueous solutions?

    <p>The density of the solution is considered to be 1 g cm⁻³. (D)</p> Signup and view all the answers

    In the example of calculating enthalpy change, why is a polystyrene cup used?

    <p>It is a good heat insulator. (C)</p> Signup and view all the answers

    What is the specific heat capacity assumed for water in calculations?

    <p>4.18 J g⁻¹ °C⁻¹ (B)</p> Signup and view all the answers

    What is indicated by the term ∆H in enthalpy calculations?

    <p>The energy change per mole of the limiting reagent. (A)</p> Signup and view all the answers

    What temperature change (ΔT) would result from an initial temperature of 18.1 °C and a maximum temperature of 24.8 °C?

    <p>6.7 °C (D)</p> Signup and view all the answers

    How can enthalpy changes be measured experimentally?

    <p>By measuring temperature changes. (D)</p> Signup and view all the answers

    What must occur for ion-solvent bonds to be formed?

    <p>Ion-ionic and solvent-solvent bonds must be broken. (A)</p> Signup and view all the answers

    Why do covalent compounds dissolve better in non-polar solvents than polar solvents?

    <p>The attraction between molecule and solvent is stronger in non-polar solvents. (C)</p> Signup and view all the answers

    Why do some covalent compounds react with water instead of dissolving?

    <p>Due to the formation of ions upon reaction. (A)</p> Signup and view all the answers

    Why are metals typically insoluble in both polar and non-polar solvents?

    <p>Metal atoms form strong metallic bonds. (C)</p> Signup and view all the answers

    What makes a gas approach ideal behavior?

    <p>Weak intermolecular forces and high temperature. (A)</p> Signup and view all the answers

    What leads to limitations of ideal gas behavior at very high pressures?

    <p>Increased intermolecular attractions become significant. (A)</p> Signup and view all the answers

    How does the kinetic-molecular model describe the liquid state?

    <p>Molecules are loosely packed and can slide past one another. (D)</p> Signup and view all the answers

    What occurs when hydrogen chloride is dissolved in water?

    <p>It forms hydrogen ions and chloride ions. (B)</p> Signup and view all the answers

    Flashcards

    Exothermic Reaction

    A reaction that releases energy to its surroundings, making the surroundings warmer. Products have less energy than reactants.

    Endothermic Reaction

    A reaction that absorbs energy from its surroundings, making the surroundings cooler. Products have more energy than reactants.

    Enthalpy Change (ΔH)

    The heat change during a chemical reaction, either absorbed or released.

    Exothermic ΔH

    Negative enthalpy change (ΔH < 0) in an exothermic reaction.

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    Endothermic ΔH

    Positive enthalpy change (ΔH > 0) in an endothermic reaction.

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    Energetic Stability

    The tendency of a system to have lower energy content.

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    Energy Level Diagram

    Diagram showing relative energy levels of reactants and products in a reaction.

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    Enthalpy

    The total energy content of a substance.

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    Kinetic Stability

    A state where a substance does not react quickly even though it has a high energy level.

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    Activation Energy

    The minimum amount of energy needed for a reaction to start.

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    Enthalpy Change Measurement

    Determining the heat energy released or absorbed during a reaction by measuring temperature changes.

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    Specific Heat Capacity

    The amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius.

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    Calculating Enthalpy Change

    Using the formula: ∆H = (mc∆T) / n, where m is mass, c is specific heat capacity, ∆T is temperature change, and n is moles.

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    Assumptions in Enthalpy Calculations

    Assuming the density of aqueous solutions is 1 g/cm³ and their specific heat capacity is the same as water.

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    Enthalpy Change of Neutralization

    The heat change when an acid and a base react to form salt and water.

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    Enthalpy Change of Combustion

    The heat change when a substance reacts with oxygen to produce energy.

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    Ion-solvent Bonds: Driving Force

    When ions dissolve, ion-solvent bonds form. The stability of this process depends on whether the energy released from forming these bonds outweighs the energy needed to break the initial ionic and solvent-solvent bonds.

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    Polar Molecules: Good Solvents for Ions

    Polar molecules have a natural attraction to ions, allowing them to dissolve effectively. The energy released from forming ion-solvent bonds compensates for the energy required to break strong ionic bonds.

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    Covalent Compounds in Non-polar Solvents

    Covalent compounds dissolve well in non-polar solvents as the energy released from forming molecule-solvent bonds is enough to overcome the weak van der Waals forces between covalent molecules.

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    Covalent Compounds in Polar Solvents

    Covalent compounds often do not dissolve in polar solvents. The energy required to break the strong forces within polar solvents is too high, making the dissolution process unstable.

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    Some Covalent Compounds: Reaction with Water

    Certain covalent compounds react chemically with water rather than dissolving. This reaction forms ions, which are then soluble.

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    Metals and Solvents

    Metals generally do not dissolve in either polar or non-polar solvents. However, some reactive metals like sodium and calcium can react with water.

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    Ideal Gas: Assumptions

    The kinetic theory of gases describes an ideal gas. It assumes that gas particles have negligible volume, no intermolecular forces, and move randomly with elastic collisions.

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    Ideal Gas: Limitations

    The ideal gas model breaks down at very high pressures and very low temperatures. At high pressure, the gas molecules are close, increasing intermolecular forces and volume. At low temperatures, the molecules move slower, making intermolecular forces more significant.

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    Description

    Test your understanding of exothermic and endothermic reactions with this quiz based on Chapter 5 of your chemistry textbook. You'll explore concepts like enthalpy change, energy relationships, and reaction types. Answer questions about reaction pathways and stability in chemical processes.

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