Unit 5 CHEM

• What is the common name for aluminium oxide?

  Alumina
• What does it mean for alumina to be amphoteric?

  It can act as an acid or a base
• How does alumina react when an acid is present?

  It reacts as a base
• How does alumina react when a base is present?

  It reacts as an acid
• What is the definition of amphoteric?

  • Substance that can act as both an acid and a base
• What is the definition of an acid?

  • A compound containing hydrogen that dissociates in water to form hydrogen ions
• What is the definition of a base?

  • A compound that reacts with an acid to form a salt and water
• How does aluminium oxide behave with hot hydrochloric acid?

  It produces aluminium chloride and water
• What is the chemical reaction of aluminium oxide with hydrochloric acid?

  $Al_2O_3 +$$6HCl \rightarrow 2AlCl_3 +$$3H_2O$
• What do aluminates form when aluminium oxide reacts with bases?

  They form compounds like sodium aluminate
• What is the reaction of aluminium oxide with sodium hydroxide?

  $Al_2O_3 +$$6NaOH +$$3H_2O \rightarrow 2Na_2Al(OH)_6$
• What is produced when hot concentrated sodium hydroxide reacts with aluminium oxide?

  Sodium tetrahydroxoaluminate
• Under what conditions is aluminium oxide chemically inert?

  When no hot acid or base is present
• What are some uses of aluminium oxide?

  • Filler
  • Paint
  • Sunscreens
  • Glass
• Why is alumina used in chromatography?

  It can act as a basic, acidic, or neutral medium
• What is the pH stability range of aluminium oxide?

  pH 2-13
• How does the amphoteric nature of alumina benefit environmental applications?

  It allows for use in clean-up and separation
• What type of metal oxides are Group 1 and Group 2 metal oxides?


  • Basic
• What happens when Group 1 and Group 2 metal oxides dissolve in water?

  They react to form metal hydroxides
• What is the result of sodium oxide reacting with water?

  $Na_2O +$$H_2O \rightarrow 2NaOH$
• What is the result of calcium oxide reacting with water?

  $CaO +$$H_2O \rightarrow Ca(OH)_2$
• What is the general reaction of metal oxides with water?

  • Metal oxides react with water to form metal hydroxides
  • This results in an alkali solution
• What are the benefits of using alumina in chromatography?


  Versatility, adjustable pH, good solute-solvent interactions, and relatively inexpensive maintenance
• Why is alumina useful as an acidic medium?


  For separating basic compounds
• What is the pH of alumina in its default state?


  Neutral
• Why is alumina useful as a basic medium?


  For separating acidic compounds that are not stable in acidic environments
• What is alumina used as in chromatography?


  A stationary phase, providing a fixed surface for separation