Chemistry grade 12

• Arrhenius base


  A substance that increases the concentration of hydroxide ions (OH-) when dissolved in water
• The Arrhenius concept assumes that hydrogen ions (H+) exist freely in water, which is not the case
• Conjugate bases


  d conjugate bases
• Identify acid-base conjugate pairs


  From given reaction
• Write equation for self-ionization


  1. Of water

  2. Of ammonia
• Amphiprotic species


  Species that can either donate or accept a proton, depending on the other reactant
• Acid (Lewis concept)


  Species that accepts an electron pair to form a bond
• Base (Lewis concept)


  Species that donates an electron pair to form a bond
• Calculate pH


  1. From [H+]

  2. From pH
• Calculate pOH


  1. From [OH-]

  2. From pOH
• Arrhenius acid


  Substance that increases the concentration of H+ (proton ion) in aqueous solution
• Arrhenius base


  Substance that increases the concentration of OH- (hydroxide ion) in aqueous solution
• Strong acid completely ionizes in aqueous solution to give H3O+ and an anion
• Strong base completely ionizes in aqueous solution to give OH- and a cation
• Strong bases


  • Hydroxides of Group IA and Group IIA elements (except Be)
• Arrhenius theory has limitations
• Brønsted-Lowry acid is a proton donor
• Brønsted-Lowry base is a proton acceptor
• Conjugate acid-base pairs differ by a single proton (H+)
• Conjugate base has one fewer H and one more minus charge than the acid
• Conjugate acid has one more H and one fewer minus charge than the base
• Stronger acid has weaker conjugate base
• Stronger base has weaker conjugate acid
• Water undergoes autoionization to form H3O+ and OH-
• Amphiprotic species


  Molecules or ions that can either donate or accept a proton, depending on the other reactant
• Amphiprotic species


  • HCO3-
  • H2O
• Lewis acid accepts an electron pair
• Lewis base donates an electron pair
• Lewis acid-base reaction


  • BF3 + NH3 -> BF3NH3
• Lewis bases


  OH-, NH3, H2O - they all have electron pairs available to donate for electron-deficient species
• Lewis acid


  Any electron-deficient molecule or positively charged species
• Lewis base


  Any molecule or negatively charged species having an excess of electrons
• Lewis acid-base reactions


  • BH3 + (CH3)2S → (CH3)2BS

  b. CaO + CO2 → CaCO3

  c. BeCl2 + 2Cl- → BeCl4-
• Identifying Lewis acid and base in reactions


  Lewis base: (CH3)2S, Lewis acid: BH3

  b. Lewis base: CaO, Lewis acid: CO2

  c. Lewis base: Cl-, Lewis acid: BeCl2
• Identifying Lewis acid and base in reactions

  Lewis base: (CH3)2O, Lewis acid: BF3

  b. Lewis base: H2O, Lewis acid: SO3
• Hydroxide ions


  Concentration of hydrogen and hydroxide ions affect acid and base strength
• pH


  Measure of acid strength
• pOH


  Measure of base strength
• Percent dissociation


  Proportion of ionized molecules, measure of acid/base strength
• Ka and Kb


  Acid and base dissociation constants, quantitative measure of acid/base strength