Focus Guide CH 13 and CH 14

Chapter 13 and 14

  • Solubility

    • Concept: "Like dissolves like"

    • Definition: This principle suggests that polar solvents will dissolve polar solutes, and non-polar solvents will dissolve non-polar solutes.

  • Henry’s Law

    • Definition: States that at a constant temperature, the amount of gas that dissolves in a liquid is proportional to the partial pressure of that gas above the liquid.

    • Formula: C=kHPC=k_{H}P

      • Where:

      • CC = concentration of the dissolved gas

      • kHk_H = Henry's Law constant specific to the gas in that solvent

      • PP = partial pressure of the gas

  • Molality

    • Definition: A measure of solute concentration defined as the number of moles of solute per kilogram of solvent.

    • Formula: m=nsolutemsolventm = \frac{n{solute}}{m{solvent}}

      • Where:

      • mm = molality

      • nsoluten_{solute} = number of moles of solute

      • msolventm_{solvent} = mass of solvent in kilograms

  • Molarity

    • Definition: A measure of solute concentration defined as the number of moles of solute per liter of solution.

    • Formula: M=nsoluteVsolutionM = \frac{n{solute}}{V{solution}}

      • Where:

      • MM = molarity

      • nsoluten_{solute} = number of moles of solute

      • VsolutionV_{solution} = volume of solution in liters

  • Mole Fraction

    • Definition: The ratio of the number of moles of one component to the total number of moles of all components in the mixture.

    • Formula: XA=nAntotalXA=\frac{nA}{n_{total}}

      • Where:

      • XAX_A = mole fraction of component A

      • nAn_A = number of moles of component A

      • ntotaln_{total} = total number of moles in the mixture

  • Osmotic Pressure

    • Definition: The pressure required to stop the flow of solvent into a solution via osmosis.

    • Formula: Π=iCRT\Pi = iCRT

      • Where:

      • Π\Pi = osmotic pressure

      • ii = van 't Hoff factor (number of particles the solute breaks into)

      • CC = molarity of the solution

      • RR = universal gas constant

      • TT = temperature in Kelvin

  • Colligative Properties

    • Definition: Properties that depend on the number of solute particles in a solution and not on the identity of the solute.

    • Examples include:

      • Boiling point elevation

      • Freezing point depression

      • Vapor pressure lowering

      • Osmotic pressure

  • Freezing Point Depression and Elevation

    • Freezing Point Depression Formula: ΔTf=Kftm\Delta Tf=Kftm

      • Where:

      • ΔTf\Delta T_f = change in freezing point

      • KfK_f = freezing point depression constant of the solvent

      • mm = molality of the solution

    • Freezing Point Elevation Formula: ΔT<em>b=K</em>bimesm\Delta T<em>b = K</em>b imes m

      • Where:

      • ΔTb\Delta T_b = change in boiling point

      • KbK_b = boiling point elevation constant of the solvent

  • Calculating Molar Mass and/or Density from FP and PB Information

    • Procedures involving the use of freezing point depression and boiling point elevation data to derive molar mass and density calculations.

  • Rate Laws

    • Determining the superscripts in a rate law:

    • It can be memorized or calculated using the method of initial rates.

    • Determining the rate law from experimental data:

    • Rate laws relate the rate of a reaction to the concentration of reactants.

    • General form of a rate law: Rate=k[A]m[B]n{Rate}=k[A]^{m}[B]^{n}

      • Where:

      • kk = rate constant

      • [A][A] and [B][B] = concentrations of reactants

      • mm and nn = reaction orders

  • Rate Constant

    • Definition: A factor that links the rate of a reaction to the concentrations of the reactants.

    • Determination from half-life:

    • Different formulas exist depending on the order of the reaction.

  • Overall Order of Reaction

    • Definition: The sum of the exponents in the rate law equation.

    • For example, in Rate=k[A]2[B]1{Rate}=k[A]^2[B]^1 , the overall order is 3.

  • Integrated Rate Laws

    • Importance of knowing and writing down the formulas for integrated rate laws.

    • For zero-order, first-order, and second-order reactions, the equations relate concentration to time.

  • Potential Energy Diagrams

    • Ability to read potential energy diagrams and understand different components:

    • Energy of reactants, products, activation energy barriers, and intermediates.

  • Rate Mechanisms

    • Definition: A sequence of elementary steps by which a reaction occurs.

    • Understanding of intermediates and catalysts:

    • Intermediates are species that are formed during the course of a reaction but are not present in the final products.

    • Catalysts are substances that increase the rate of a reaction without being consumed.

  • Molecularity

    • Definition: The number of molecules that participate in an elementary reaction.

    • Categories include unimolecular, bimolecular, and trimolecular steps.

  • Equilibrium Constant

    • Definition: A ratio of the concentration of products to reactants at equilibrium.

    • Formula: Keq=[products][reactants]K_{eq} = \frac{[products]}{[reactants]}

    • Effect of changing conditions:

    • If a reaction is reversed, halved, or doubled, the equilibrium constant adjusts accordingly.

  • Definitions of Various Catalysts

    • Explanation of types of catalysts:

    • Homogeneous catalysts: Present in the same phase as the reactants.

    • Heterogeneous catalysts: Present in a different phase from the reactants.

    • Enzymes: Biological catalysts that increase reaction rates under mild conditions.