8th Grade Home



Activity 1
Decomposition Reactions

NaHCO3 --->  Na2CO3 + CO2 + H2O
sodium bicarbonate ---> sodium carbonate + carbon dioxide + water
       
Materials needed for each station:
Part A:
 Part B:
  • 1 Test Tube one hole stopper
  • 2 Glass Pyrex Test Tube (medium)
  • 1 Glass Pyrex Test Tube (small)
  • 1 piece rigid tubing, 30.5 cm
  • 1 piece flexbile tubing, 30.5 cm
  • small amount of Sodium Bicarbonate (NaHCO3)
  • 1 Test Tube rack
  • 1 Test Tube clamp
  • 2-3 mL bromothymol blue (acid indicator) in small test tube
  • 1 flame source
  • Sodium Carbonate from Part A: ( Na2CO3 )
  • 1 crucible with lid
  • 2-3 mL water in medium test tube
  • 1 strip of wide range pH paper
  • 1 ring or burner stand
  • 1 test tube clamp
  • 1 flame source

Procedures -- Part A:
  1. Set up your testing apparatus.  Place a small amount of sodium bicarbonate into the glass test tbe and 2-3 mL of bromothymol blue (BTB) into the small test tube at the other end of the set-up.  Place the BTB into the plastic tube holder, and make sure that all of the connections between the stopper and lengths of tubing are secure.
  2. Use a test tube clamp to heat the sodium bicarbonate in the glass test tube.  As carbon dioxide and water gas is produced, bubbles travel up through the BTB.  The BTB should turn orange/yellow in the presence of carbon dioxide.  Note how long it takes for this reaction to occur, and record your answer in your Lab book.
Procedures -- Part B:
  1. Place the product (sodium carbonate) from the test tube in Part A into a crucible with a lid.  Close the lid of the crucible, place the crucible on a stand, and then heat for 5 minutes.
  2. Dissolve the heated sodium carbonate by transferring it into a test tube containing 2-3 mL of water.  Gently stir the solution until it is fully dissolved.
  3. When dissolved in water, sodium carbonate produces a basic hydroxide, hich will show as a base when tested with pH paper.  Test the pH of the solution with a wide range pH strip.  Compare your reading to the color indicator on the pH strip jar.  Record the approximate pH of your solution.
  4. Complete the Results Questions for Part A and Part B.