Qualitative analysis

• What does colour change, effervescence and light tell you about a reaction ?

  The reaction is irreversible and new products are formed.
• What do you get when an acid reacts with a carbonate ?

  salt + water + carbon dioxide
• What are observations in a carbonate test ?

  effervecence
• How is the presence of CO2 confirmed ?

  Bubble the gas through lime water and if the lime water turns cloudy then CO2 is present.
• What is the formula for lime water ?

  Ca(OH)2
• What is formed when carbonate reacts with lime water ?

  CaCO3 (s)
• What is observed in a positive sulfate test ?

  white ppt
• What is the equation for barium sulfate ?

  Ba*2+ (aq) + SO4*2- (aq) --> BaSO4 (s)
• What is added for a sulfate test ?

  Ba(NO3)2
• What is added for a carbonate test ?

  HNO3
• What is added for a halide test ?

  AgNO3
• What is the ionic equation for the halide test of chlorine ?

  Ag+ (aq) + Cl- (aq) --> AgCl (s)
• What is the colour of the preciptate for the halogens in a halide test ?

  Cl- = white

  Br- = cream

  I- = yellow
• What is the solubility of Cl-, Br- and I- in ammonium ?

  Cl- = soluble in dilute ammonium

  Br- = soluble in concentrated ammonium

  I- = insoluble
• What is added to test for a cation ?

  NaOH
• What is the ionic equation for the reaction for the test for cations (NH4+) ?

  NH4+ (aq) + OH- (aq) --> NH3 (g) + H2O (l)
• Describe the method used to test for ammonium ions ?

  1. Add NaOH (aq) to solution
  2. Ammonia gas is produced - no effervescence because ammonia is soluble in water
  3. Heat to release ammonia gas
  4. Distinctive smell or damp red litmus paper will turn blue = ammonium ions present