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 (D)</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

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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., Clâ‚‚).
  • Strong Electrolyte: Dissociates completely in water (e.g., NHâ‚„NO₃).
  • 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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