Acids and Alkalis

• Classifying acids

  pH < 7

  Strong acids pH 1 -3

  Weak acids pH 1-6

  The lower the pH, the more acidic the solution is
• Classifying Alkalis

  • pH > 7
  • Strong alkalis pH 11-14
  • Weak alkalis pH 8-10
  • The higher the pH, the more alkaline a solution is
• Testing pH : Universal Indicator

  • a mixture of dyes that changes based on the pH of a solution.
  • red TO yellow = acidic
  • green neutral
  • blue TO purple = alkaline
• A more accurate test for pH

  • pH probe / meter
  • Electronic measure of pH
  • Placed in testing solution, provides a digital display / numerical value
• Why is a pH probe better than a universal indicator?

  • more accurate
  • more precise = higher resolution
  • not affected by subjectivity
• Dissolving acids

  • Acids form hydrogen ions (H+) when dissolved in water / aqueous solution.
• Dissolving alkalis

  • Alkalis form hydroxide ions (OH-) when dissolved in water / aqueous solution.
• Acids

  H+
• Alkali

  OH-
• Neutralisation reaction

  Alkali + acid --> salt + water
• Neutralisation reaction in terms of IONS

  • OH- + H+ --> H2O
• Alkaline solution + acidic solution

  • forms a solution that is neutral, a pH of 7
• pH

  • measure of how acidic or alkaline a solution is
• Neutralisation reaction example

  • Lithium hydroxide + hydrochloric acid --> lithium chloride + water
  • LiOH + HCl --> LiCl + H2O
• Sulfuric acid and charge

  • H2SO4
  • 2- charge
• Alkalis

  • Soluble metal hydroxides
  • Soluble metal oxides
• Bases

  • Insoluble metal hydroxides
  • Insoluble metal oxides
• State of OH-

  Aqueous
• State of H+

  • Aqueous