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Chemistry LibreTexts

Example Final Conceptual Questions

  • Page ID
    306159
  • Topical Questions: (these should be mastered so that you can answer them quickly without thinking)

    Thermodynamics

    • What is the difference between a “microstate” and a “macrostate”?
    • Explain the concept of entropy
    • Explain why is an isothermal expansion of an ideal gas is spontaneous when the change in internal energy is zero
    • Can the absolute zero of entropy be determined?
    • How does increasing temperature affect the entropy of a system? Why?
    • What has the higher entropy, liquid water or water vapor? Why?
    • What has the higher entropy, \(NO (g)\) or \(NO_2 (g)\)?
    • What is the second law of thermodynamics?
    • What characterizes a spontaneous reaction?
    • Why do we introduce Gibbs free energy?
    • What is ΔG at equilibrium?
    • What drives a chemical reaction?
    • Why are some reactions spontaneous only at high temperatures while others are spontaneous only at low temperatures?
    • What is the definition of the free energy of formation?
    • What does the sign of the standard free energy of a compound tell you?
    • What is the standard state?
    • How does ΔGº relate to ΔG at nonstandard conditions?
    • Explain how the equilibrium constant and Gibbs energy are related
    • What is the temperature dependence of K?
    • For each of these processes state if they are endothermic or exothermic, cause an increase or a decrease in entropy, and whether the process occurs spontaneously. Not all of them has unique answers, describe what the answers will depend on
      • Condensation of a gas to a liquid
      • Dissolution of an ionic solid
      • Mixing of water and oil
      • Mixing of water and ethanol
      • Melting of an ice cube
      • \(H_2 (g) + O_2 (g) → H_2O (l)\)
      • Isothermal expansion of an ideal gas

    Liquids, Solids, and Intermolecular Forces

    • Define the following terms
      • Cohesive forces (forces between like molecules)
      • Adhesive forces (forces between unlike molecules)
      • Surface tension
      • Viscosity
    • Classify IMFs into one of four categories
      • Permanent electrostatic-Permanent electrostatic
      • Permanent Electrostatic-Induced electrostatic
      • Spontaneous Electrostatic-Induced Electrostatic (Dispersion)
      • Repulsion
    • Define Polarizability
    • What IMF category(ies) does polarizability play a strong role in?
    • What factors influence the magnitude of polarizability?
    • What is the difference between London force and Dispersion force?
    • Under what conditions will hydrogen bonding be observed?
    • How do the IMFs strengths compare to covalent bonding strengths?
    • What is the origin of the repulsion force?
    • In what systems are repulsion forces not involved?
    • Which IMF has the longest range of interaction (be specific)?
    • Which IMF has the shortest range of interaction (be specific)?
    • What is a hydrogen bond donor?
    • What is a hydrogen bond acceptor?
    • Give two examples of phases that do not correspond to differing states.
    • What is the definition of vapor pressure?
    • How is vapor pressure related to IMFs?
    • What is the definition of boiling?
      • What are two ways that you can make a liquid boil?
    • Define
      • critical point
      • triple point
      • melting
      • melting point
      • enthalpy of fusion
      • heat of fusion
      • enthalpy of vaporization
      • heat of vaporization
      • enthalpy of sublimation
      • heat of sublimation
      • Supercritical fluids
      • Phase transitions
    • How is ·Enthalpy of vaporization related to ·Enthalpy of sublimation?
      • What is the origin of this relationship?
    • What are the differences between the phase diagram for water and for \(\ce{CO2}\)?
    • When would you use the Claussius-Clapeyron equation?
    • When would you use the Clapeyron equation?
    • What is the difference between the two? What is the approximation used to derive the Claussius-Clapeyron equation?

    Solutions

    • What are the definitions of the following concentration units:
      • Mass percent?
      • ppm?
      • Mole fraction?
      • Molarity?
      • Molality?
    • Which concentration units are temperature dependent?
    • Which concentration units are temperature independent?
    • What determines if the enthalpy of solution is positive or negative?
    • What is an ideal solution?
    • What drives the formation of an ideal solution?
    • Crystal lattice energies are typically very strong. Give two reasons why many salts nevertheless are easily soluble in water
    • How does the solubility of gases depend of the partial pressure of the gas?
    • What is the definition of a lattice energy?
    • What is the definition of a Solvation energy?
    • Definition between real and ideal solutions
    • Definition of Activities
    • How does the vapor pressure of an ideal solution depend on composition?
    • Is the composition of the vapor phase and liquid phase for a solution different? Why?
    • What is fractional distillation? How does it work?
    • What is an azeotrope?
    • What is osmotic pressure?
    • What is reversed osmosis?
    • What are colligative effects? Which four did we discuss in class?
    • Using a phase diagram, explain how freezing point depression and boiling point elevation are consequences of Raoult’s law
    • What is the van ’t Hoff factor?
    • What is Henry's law?
      • Is it applicable for ideal solutions?
    • What is Raoult's law?
      • Is it applicable for ideal solutions
      • Is Raoult's law applicable for volatile or non-volatile solutions? Or both or neither?
    • What is the definition of a saturated solution?
    • What does supersaturated mean?
    • Does a solid have a vapor pressure?
    • Is vaporization an endothermic or an exothermic process?

    Equilibria

    • What is a dynamic equilibrium? How does it compare to static equilibria?
    • What is the law of mass action?
    • What is the definition of \(K_c\)?
    • What are the units of \(K_c\)?
    • How does the equilibrium constant depend on the initial conditions?
    • What is the activity?
    • If a reaction can be written as the sum of two reactions with known equilibrium constants, how can you determine the equilibrium constant for the overall reaction?
    • What is \(K_p\)?
    • What is the difference between \(K_p\) and \(K_c\)?
    • How do pure liquids and pure solids enter the equilibrium constant? Why?
    • What can you tell from the size of the equilibrium constant?
    • What is the difference between K and Q?
    • How can you predict the direction of a reaction knowing K and Q?
    • If you add more reactant to a reaction that is initially at equilibrium, what will happen?
    • If you increase the partial pressures equally of all gases involved in a reaction that is initially at equilibrium, what will happen?
    • According to Le Chatelier’s principle, what happens to an exothermic reaction if the temperature is increased? Does K change?
    • If Q >K reaction, does the reaction (as written) go to the left, right or not change?
    • If Q <K reaction, does the reaction (as written) go to the left, right or not change?
    • If Q =K reaction, does the reaction (as written) go to the left, right or not change?

    Acids and Bases

    • Is an aqueous solution of NaCl acidic or basic? Why?
    • Is an aqueous solution of NH4Cl acidic or basic? Why?
    • What is the pH of a solution containing 0.1 M HCl and 0.1 M acetic acid? What is the concentration of acetic acid and acetate (the conjugate base) in this solution?
    • What is a buffer solution?
    • How do you make a buffer solution?
    • What is the pH of a buffer solution?
    • What is the buffer capacity? What does it depend on?
    • What characterizes an acid-base indicator ?
    • What is the equivalence point in a titration?
    • What is pH halfway to the equivalence point during a titration of a weak base with a strong acid?
    • How are pH and pOH related?
    • How is the pKa of an acid related to the pKb of the conjugate base?
    • What is pH for a 0.1M solution of HNO3?
    • What is pH for a 10-8 M solution of HNO3?
    • What defines a strong acid?
    • Name three strong acids
    • Which one is the stronger acid: Acetic acid (pKa= 4.74) or formic acid (pKa= 3.74)?
      • Which one is the stronger base: the acetate ion (\(C_2H_3O_2^−\)) or formate ion (\(CHO_2^−\))?
    • When can you simplify the solution of an equilibrium calculation (by assuming that the change x is small)?

    Solubility

    • What is the definition of the solubility product?
    • How does the solubility product relate to the solubility defined in chapter 13?
    • How do you determine if precipitation occurs in a solution?
    • What is the common-ion effect?
    • Explain why the solubility of a sparingly soluble salt increases when a highly soluble salt of spectator ions is added to the solution?
    • What is “salting out”?
    • Give one explanation for why “salting out” occurs
    • What is the activity coefficient?
    • Why is Ksp not constant?
    • What is fractional precipitation?
    • For what types of salts is the solubility affected by pH?
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