Chapter 9.1: The Acid-Base Properties of Salt Solutions

• Acidic and Basic Properties of Salts

  • Salts that dissolve and form neutral solutions

    • Strong acid with water:

      • Product is a weak base: no effect on pH

    • Strong base with water

      • Product is a weak acid: no effect on pH

  • Salts that dissolve and form basic solutions

    • Weak base with water:

      • Conjugate acid is strong acid: pH is less than 7

      • Salts of weak bases and strong acids dissolve in water and form acidic solutions

  • Salts of weak bases and weak acids

    • Weak acid with water

      • The conjugate base is the strong base: pH more than 7

      • Salts of strong bases and weak acid dissolve in water and form basic solutions

  • Salts of weak bases and weak acids

    • If Kb > Ka solution is acidic

    • If Kb > Ka solution is basic

• equivalence point in the titration occurs when just enough acid and base have been mixed for a complete reaction to occur

  • no excess of either reactant

• The point in a titration at which an indicator changes color is called the end-point

Chapter 9.2: Solubility Equilibrium

• Change is favored when ∆G is negative

  • Salt dissolving increases the entropy of the system

• The solubility product constant, Ksp: equilibrium between solid and respective ions in solutions

  • Ksp = [A+]a [B−]b

  • Constant at a given temperature

• Common-ion effect applies to buffer

  • Use Ka instead of Ksp

Chapter 9.3: Predicting the formation of a precipitate

• Ion product, Qsp: an expression that is identical to the solubility product constant, but its value is calculated using concentrations that are not necessarily those at equilibrium If Qsp < Ksp: product of the concentration of the ions is smaller than it is at equilibrium Systema process in which ions are selectively precipitated from solution, leaving other ions attains equilibrium by moving to the right favoring dissociation More dissolve can dissolve If Qsp = Ksp: the system is at equilibrium more solid solve No precipitate forms If Qsp > Ksp: product of the concentration of ions is greater than it would be in equilibrium System attains equilibrium by moving to the left favoring precipitation precipitates forms until equilibrium is reached

• Analytical Applications of Precipitate Reactions: Used to find ions ignoring other ions present

  • Qualitative analysis: branch of analytical chemistry that involves identifying elements, compounds, and ions in samples of unknown or uncertain composition

    • Spectrophotometers

  • Quantitative analysis: analytical chemists determine how much of a compound, element, or ion is in a sample