the pH scale

• pH scale


  Used to measure the strength of acids and bases and to determine which solution is more acidic or more basic (alkaline)
• Acids


  Substances with a pH value less than 7
• Bases/Alkalis


  Substances with a pH value greater than 7
• Lower pH


  More acidic substance is
• Higher pH


  Less acidic substance is
• Lower pH


  Less basic/alkaline substance is
• Higher pH


  More basic/alkaline substance is
• PH increases


  Concentration of H⁺ ions decreases
• PH decreases


  Concentration of H⁺ ions increases
• PH increases

  Concentration of OH^- ions increases
• PH decreases


  Concentration of OH ions decreases
• Neutral solution


  Concentration of H⁺ ions is equal to OH^- concentration
• Water molecule


  Isn't ionic, but is able to ionize to a very small extent
• Water ionization


  H₂O ⇌ H+ + OH-
• Any water solution contains both hydrogen and hydroxide ions
• Concentration of H+ (hydrogen ion)


  Inverse relationship with concentration of OH- (hydroxide ion)
• pH


  Measure of the acidity or basicity of a solution
• pH 7 is a neutral solution
• Concentration of H+


  Decreases as pH increases
• Concentration of OH-


  Increases as pH increases
• In a pure/neutral solution, [H+] = [OH-]
• Acidic solution


  [H+] > [OH-]
• Basic solution


  [OH-] > [H+]
• pH + pOH = 14 (always)
• Calculating pH from [H+]

  pH = -log[H+]
• pH is a logarithmic scale
• Each pH unit change represents a 10-fold change in [H+]
• The water molecule isn't ionic, but is able to ionize to a very small extent
• Water ionization


  H2O + H2O ⇌ H3O+ + OH-
• Any water solution contains both hydrogen and hydroxide ions
• pH scale


  Measure of the acidity or basicity of a solution
• Neutral solution has a pH of 7
• Acidic solutions have a pH less than 7 (the lower the pH, the more acidic)
• Basic solutions have a pH greater than 7 (the higher the pH, the more basic)
• pH


  • log[H+]
• Finding pH from pOH

  pH = 14 - pOH
• pH is a logarithmic scale, each unit change represents a factor of 10 change in H+ concentration