# Acids and Bases

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• ACIDS AND BASES
• Bronsted-Lowry Acids and Bases
• Acid = Proton donor
• Base = Proton acceptor
• Acid-base equilibria = transfer of protons
• pH of Strong Acids
• pH = -Log10[H+]
• [H+] = 10-pH
• pH of Strong Bases
• Ionic Product of Water
• Water is weakly dissociated
• Kw = [H+][OH-]
• [H+] = Kw/[OH-]
• pH of Strong Bases
• Ionic Product of Water
• Water is weakly dissociated
• Kw = [H+][OH-]
• [H+] = Kw/[OH-]
• Buffer Solutions
• Resists changes in pH when small amounts of acid or alkali are added, or when it is diluted
• At an equilibrium
• pH of buffer solutions
• [H+] = Ka[acid]/[salt]
• pH = pKa x Log10([salt]/[acid])
• pH Curves
• Titration Calculations
• Strong acid, strong base
• -Calculate number of moles of H+ ions and OH- ions in each solution  -Work out which ion is in excess -Calculate the total volume of the mixture -Calculate the concentration of the excess ion -Calculate pH
• Weak acid, strong base
• -Calculate number of moles of weak acid and OH- ions in each solution -Work out which one is in excess -Calculate the total volume of the mixture -Calculate [H+] and pH from excess ions
• pH of Weak Acids
• Weak acids and bases only dissociate slightly in aqueous solution
• Ka = [H+][A-]/[HA]
• For a weak acid in aqueous solution, [H+] = [A-]
• So Ka = [H+][H+]/[HA]
• Ka = Acid dissociation constant
• pKa = -Log10Ka