AP Chem Chapter 8

Acids and Bases Overview

• Bronsted-Lowry Theory:

  • Acid: Proton donor

  • Base: Proton acceptor

• Arrhenius Theory:

  • Acid: Produces H3O+ in water

  • Base: Produces OH- in water

• Key Concepts:

  • Acid-base reactions occur in aqueous solutions.

  • Strong acids and bases fully ionize; weak acids and bases ionize partially.

• Equilibrium Constants:

  • Kw (autoionization of water) = 1×10^-14 at 298K

  • pKw = 14 = pKa + pKb

• Mixture Behaviors:

  • Strong Acid + Strong Base: pH from excess reagent.

  • Weak Acid + Strong Base: Buffer if weak acid excess; pH based on excess OH- if strong base excess.

  • Weak Base + Strong Acid: Buffer if weak base excess; pH from excess H3O+ if strong acid excess.

  • Weak Acid + Weak Base: Reaches equilibrium state.

• Titrations:

  • Equivalence point: the number of moles of titrations added is equal to the number of moles of analyte present

  • Polyprotic Acid: An acid that donates multiple protons and has a dissociation that occurs in steps

  • pH is 5-6 if Methyl orange is used as an indicator

    • If it’s red its in an acid

    • If it’s in a base it’s yellow

  • pH is 6-7 if Methyl red is used as an indicator

    • If it’s red and it’s in an acid

    • If it’s yellow and it’s in a base

  • pH is 7-8 if Litmus is used as an indicator

    • If it’s red and it’s in an acid

    • If it’s blue and it’s in a base

  • pH is 9-10 if Phenolphthalein is used as an indicator

    • If it’s colorless its in an acid

    • If it’s pink and it’s in a base

  • An acid with more than one H+ will have multiple equivalence points and the titration curve will have multiple vertical points

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• Structure of Acids/Bases:

  • Strong acids have very weak conjugate bases and vice versa

  • Electronegative elements tend to stabilize the conjugate bases relative to the conjugate acid and increase the acid strength