Acids and Bases

• Acids are compounds that dissolve in water to produce hydrogen ions.

  For example...

  Strong acids= Hydrochloric acid or Sulfuric acid

  Weak acids= Ethanoic acid
• Bases are a substance that reacts with an acid to produce salt and water, a neutralisation reaction. They are insoluble in water.

  Metal oxides are also bases as they dissolve in acid to produce salt and water.
• Alkalis are soluble bases, they dissolve in water to produce hydroxide ions.

  For example...

  Strong alkali= Sodium hydroxide or Potassium hydroxide
• Bronsted-Lowry theory of acids and bases:

  • Bronsted-Lowry acid= Proton donor
  • Bronsted-Lowry base= Proton acceptor
  • Strong acids completely dissociate in aqueous solutions= ionise completely.
  • Weak acids partially dissociate in aqueous solution= ionise partially.
  • Monoprotic= Donates one electron per molecule.
  • Diprotic= Donates two electrons per molecule.
• • Monoprotic= Donates one electron per molecule.

  Hydrochloric acid= Strong monotropic acid, 1 mol of HCl produces 1 mol of H+
• • Diprotic= Donates two electrons per molecule.

  Ethanoic acid= Weak monoprotic acid, 1 mol of C2H4O2 produces 1 mol of  H+

  Sulfuric acid= Strong diprotic acid, 1 mol of H2SO4 produces 2 mol of H+
• pH= The concentration of hydrogen ions in aqueous solution covers a very wide range. The pH scale is used as a measure of hydrogen ion concentration, showing acidity or alkalinity.

  Acidic= High concentration of H+

  Alkaline= Low concentration of H+
• pH equations:

  A) pH

  B) pOH

  C) log10

  D) pOH

  E) 14

  
• Ionic products of water:

  Water slightly dissociates to ions as an equilibrium with its own equilibrium constant , Kw. 

  H2O ⇄ H+ + OH-

  • At room temperature (25oC), Kw has a constant of 1x10-14. However as temperature changes, Kw changes.
  • Temperature increase= more H+ ions produced= Water becomes more acidic
• For pure water Kw=[H+]2 or Kw=[OH-]2 because ions are the only ions present in pure water.
• Ionic water equations:

  A) neutral

  B) acidic

  C) basic

  D) Kw

  E) H

  F) OH

  G) Kw

  H) OH-

  I) H+

  J) Kw

  
• pH of water:

  pKw = pH + pOH

  pOH = -log10[OH-] 
• Weak acid and bases partially dissociate in an aqueous solution to form an equilibrium mixture, with its own equilibrium constant, Ka.