Demonstration of sodium carbonate derived from sodium hydrogen carbonate

Chemicals needed

sodium hydrogen carbonate

Hazardous substance information

sodium carbonate Xi  R 36    S (2)-22-26

Equipment necessary

tripod
clay triangle
evaporating dish
gas burner
crucible tongs
glass rod
scale (accurate to 0.1 g minimally)

Test procedure

• Measure the weight of the empty dish and record this.
• Weigh into the dish 8.4 g of sodium hydrogen carbonate.
• Place the clay triangle on to the tripod, place the burner under this, place the dish on to the clay triangle (paying attention to stability!)
• Heat for four minutes three times with a powerful flame. In-between reduce the flame and thoroughly mix the contents of the dish with a glass rod, firmly holding the dish with tongs.
• Extinguish the burner and let the dish cool.
• Measure the weight of the contents of the dish (weight minus weight of dish). One obtains 5.3 g of pure sodium carbonate.

Disposal

• As the resultant sodium carbonate is pure and dry, one should store it in a properly labeled bottle for further experiments. Otherwise one can dispose of it together with water in the drainage.

Elucidation

2 NaHCO3 --> Na2CO3 + CO2 + H2O

Heating causes the splitting off of carbon dioxide and water, which then volatilize so that no back reaction can occur.The molecular weight ratio of 2 NaHCO3 / Na2CO3 is 168 / 106, which corresponds exactly to the observed substance weight ratio of 8.4 / 5.3 entspricht. The reaction proceeds therefore quantitatively.

Photos

Heating of sodium hydrogen carbonate

Literature

after experiment 992S, "Quantitative Überführung von Natriumhydrogenkarbonat in Natriumkarbonat", p. 244,[2]