Chemistry Exam 4 Flashcards
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Questions and Answers

Which of the following phase changes is endothermic?

  • Condensation
  • Melting
  • Sublimation (correct)
  • Freezing

    • Which one of the following phase changes would be exothermic?

  • Sublimation
  • Vaporization
  • Melting
  • Condensation (correct)

    • What phase change is represented by the transition from A to C?

    sublimation

    Which of the following phases does a sample of water exist in at its triple point?

    <p>solid, liquid, and gas</p> Signup and view all the answers

    Which best explains why the meniscus of mercury in a glass tube is convex?

    <p>high surface tension</p> Signup and view all the answers

    What is surface tension?

    <p>energy needed to separate the molecules at the surface of a liquid</p> Signup and view all the answers

    What is a saturated solution?

    <p>a solution that contains the maximum concentration of a solute possible at a given temperature</p> Signup and view all the answers

    What is an unsaturated solution?

    <p>a solution that contains less than the maximum amount of solute at a given temperature</p> Signup and view all the answers

    What is a supersaturated solution?

    <p>a solution that contains more than the maximum quantity of solute predicted to be soluble</p> Signup and view all the answers

    What is an Arrhenius acid?

    <p>produces hydronium ions when dissociated in water</p> Signup and view all the answers

    What is a Bronsted-Lowry acid?

    <p>a substance that donates a proton to another substance</p> Signup and view all the answers

    What is a Bronsted-Lowry base?

    <p>a substance that can accept a proton</p> Signup and view all the answers

    Acid + base ->

    <p>water + salt</p> Signup and view all the answers

    Which of the following can be classified as a strong base?

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

    What are the products of a strong acid/strong base reaction?

    <p>water and salt</p> Signup and view all the answers

    What is oxidation in terms of electron transfer?

    <p>loss of electrons</p> Signup and view all the answers

    What is reduction?

    <p>gain of electrons</p> Signup and view all the answers

    What does the oxidation number (ON) represent for atoms in pure elements?

    <p>0</p> Signup and view all the answers

    What is a nonelectrolyte?

    <p>a substance that does not ionize in water</p> Signup and view all the answers

    What is a strong electrolyte?

    <p>a substance that completely dissociates into ions in water</p> Signup and view all the answers

    Which compound can be classified as a weak electrolyte?

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

    What does endothermic mean?

    <p>add heat</p> Signup and view all the answers

    What does exothermic mean?

    <p>releases heat</p> Signup and view all the answers

    1 dietary cal =

    <p>1 kcal</p> Signup and view all the answers

    How many calories are in fats per gram?

    <p>9 calories</p> Signup and view all the answers

    How many kilocalories are in carbohydrates per gram?

    <p>4 kcal</p> Signup and view all the answers

    How many kilocalories are in protein per gram?

    <p>4 kcal</p> Signup and view all the answers

    What is the oxidation number of hydrogen?

    <p>+1</p> Signup and view all the answers

    What is the oxidation number of oxygen?

    <p>-2</p> Signup and view all the answers

    What do oxidizing agents do?

    <p>gain electrons and are reduced</p> Signup and view all the answers

    What do reducing agents do?

    <p>lose electrons and are oxidized</p> Signup and view all the answers

    What is sodium oxidation number?

    <p>1</p> Signup and view all the answers

    4.184 j =

    <p>1 cal</p> Signup and view all the answers

    100 j per

    <p>1 kj</p> Signup and view all the answers

    4.185 kj =

    <p>1 kcal</p> Signup and view all the answers

    1000 cal =

    <p>1 kcal</p> Signup and view all the answers

    When molecules absorb heat, there is an increase in

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

    What does the First Law of Thermodynamics tell us?

    <p>the energy of the universe is a constant</p> Signup and view all the answers

    An exothermic reaction causes the surroundings to

    <p>warm up</p> Signup and view all the answers

    DeltaH =

    <p>products - reactants</p> Signup and view all the answers

    Study Notes

    Phase Changes

    • Endothermic Phase Change: Sublimation is an endothermic process where a solid transitions directly to a gas, requiring energy input.
    • Exothermic Phase Change: Condensation is an exothermic process in which gas transitions to liquid, releasing energy as molecules become closer together.
    • Triple Point of Water: The triple point is defined as the temperature and pressure where solid, liquid, and gas phases coexist.

    Surface Tension

    • Convex Meniscus of Mercury: High surface tension in mercury creates a convex meniscus as mercury molecules are more attracted to each other than to the glass surface.
    • Surface Tension Definition: The energy required to separate molecules at the surface of a liquid.

    Solutions

    • Saturated Solution: Contains the maximum concentration of solute possible at a specific temperature.
    • Unsaturated Solution: Contains less solute than the maximum at a given temperature.
    • Supersaturated Solution: Contains more solute than predicted to be soluble at a given temperature.

    Acids and Bases

    • Arrhenius Acid: Produces hydronium ions when dissolved in water.
    • Brønsted-Lowry Acid: A substance that donates protons (H+ ions).
    • Brønsted-Lowry Base: A substance that accepts protons.

    Reactions

    • Acid-Base Reaction Products: The reaction between an acid and a base produces water and a salt.
    • Strong Bases: Examples include LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2.
    • Products of Strong Acid/Strong Base Reaction: Resulting products are water and salt.

    Oxidation and Reduction

    • Oxidation: Involves the gain of oxygen, loss of electrons, and an increase in oxidation state.
    • Reduction: Involves loss of oxygen, gain of electrons, and a decrease in oxidation state.

    Oxidation Number Rules

    • General Oxidation Number (ON) Rules:
      • ON is 0 for pure elements.
      • ON equals the charge for monatomic ions.
      • Hydrogen has an ON of +1.
      • The sum of ON in a neutral molecule is 0.

    Electrolytes

    • Nonelectrolyte: A substance that does not form ions in aqueous solution (e.g., Cl₂).
    • Strong Electrolyte: Dissociates completely in water (e.g., NH₄NO₃).
    • Weak Electrolyte: Partially ionizes in water (e.g., HF).

    Thermodynamics

    • Endothermic Process: Heat is absorbed during the process.
    • Exothermic Process: Heat is released, causing the surroundings to warm up.
    • First Law of Thermodynamics: States that energy in the universe is constant.

    Key Energy Concepts

    • Caloric Values:
      • Fats: 9 kcal/g
      • Carbohydrates: 4 kcal/g
      • Proteins: 4 kcal/g
    • Conversion Factors:
      • 1 dietary calorie (cal) = 1 kilocalorie (kcal)
      • 4.184 joules (J) = 1 calorie (cal)
      • 1000 calories (cal) = 1 kilocalorie (kcal)

    Molecular Kinetics

    • Heat Absorption: Leads to an increase in the kinetic energy of molecules.
    • ΔH Calculation: Change in enthalpy is calculated as products minus reactants.

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    Description

    Test your knowledge with these flashcards focused on phase changes in chemistry. This quiz covers both endothermic and exothermic processes, emphasizing key concepts like sublimation and condensation. Ideal for students preparing for an exam.

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