Identifying the Products of a Chemical Reaction

• What happens when alkali metals react with cold water?


  • Lithium - Moves around the surface of the water, fizzing furiously
  • Sodium - Moves around the surface of the water + melts
  • Potassium - Moves around the water, melts + ignites the hydrogen gas being produced
  • Rubidium + Caesium - React violently with the water + tend to explode
• What is a halogen displacement reaction?


  A more reactive halogen can displace a less reactive one from a salt solution.
• How can you tell if halogen displacement has occurred?


  There is a colour change.
• What are the colours of halogens at room temperature?


  • Fluorine - A toxic, yellow gas
  • Chlorine - A toxic, dense, green gas
  • Bromine - A dense red-brown liquid, but will form a toxic red-brown vapour when it is warmed
  • Iodine - A dark, grey solid but will form a toxic, purple iodine vapour when it is warmed
• How do you know what a coloured compound contains?

  The colour of it depends on the transition metal ion it contains.

  • Iron(11) - Light green
  • Iron(111) - Orange/Brown
  • Copper (Cu2+) - Blue
  • Cobalt - Dark Blue
• What is a metal displacement reaction?


  When a more reactive metal displaces a less reactive one from its compound.
• How would you know if a displacement has occurred?


  A colour change
• What are the trends in reactivity?

  • Reactivity increases down metal groups (e.g. group 1, 2)
  • Reactivity deceases down non-metal groups (e.g. group 6, 7)
  • Francium + Fluorine are the most reactive
• What is the test for hydrogen?


  Squeaky Pop Test - Put a lit splint at the end of the test tube and if it makes a squeaky pop, there is hydrogen.
• What is the test for oxygen?


  Lit Splint - Put a smoldering splint next to a test tube and if it re-lights, it contains oxygen.
• What is the test for carbon dioxide?


  Cloudy Limewater - Put the gas into the clear limewater, and if it turns cloudy, it contains carbon dioxide.
• What is the test for chlorine?


  Litmus Paper - Put damp blue litmus paper into the gas and if it goes from red to white, it contains chlorine gas.
• What is the test for water?

  Cobalt Chloride Paper - Cobalt Chloride paper turning from blue to pink
• What is the test for cations?


  Flame Test

  • Dip a nichrome wire into HCl (to clean) and into the Bunsen burner flame
  • Dip it back into the HCl before putting it into the test solution
  • Then check the colour of the flame before rinsing the wire in distilled water
• What are the colours of the flame in the flame test?


  • Li+ - Scarlet Red
  • Na+ - Yellow
  • K+ - Lilac
  • Ca2+ - Brick Red
  • Cu2+ - Green with blue flakes