Aim:
To find out whether there is a relationship
between the ease of decomposition with the position of metals in the reactivity
series.
Apparatus:
Retort stand
Bunsen burner
2 test tubes
Delivery tube
Spatula
Chemicals:
Metal carbonate (eg copper
carbonate, sodium carbonate)
Limewater
Procedure:
1) Put 2 spatula of the metal carbonate into
a test tube and attach the test tube to the retort stand
2) Fit the delivery onto the test tube
3) Half fill the second test tube with
limewater and make sure the end of the delivery tube is dipped into the second
test tube, inside the limewater.
4) Heat the solid gently
5) Write down all observation
6) Repeat step 1 to 5 with the other metal
carbonate
Observations:
|
Carbonate
|
Colour before
heating
|
Colour after
heating
|
Gas given out
|
Ease of
decomposition
|
|
Potassium carbonate
|
white
|
white
|
none
|
Very difficult
|
|
Sodium carbonate
|
white
|
white
|
none
|
Very difficult
|
|
Zinc carbonate
|
white
|
yellow when hot, white when cool
|
carbon dioxide
|
fairly easy
|
|
Lead carbonate
|
white
|
yellow
|
carbon dioxide
|
fairly easy
|
|
Copper carbonate
|
green
|
black
|
carbon dioxide
|
easy
|
sodium and
potassium carbonates give no carbon dioxide or any other sign that
decomposition has taken place, even after prolonged heating.
Those metal carbonates which do decompose
leave a residue of the metal oxide and gives out carbon dioxide in the process
chemical eqn: CuCO3 → CuO + CO2
Precautions:
-Wear eye protection.
-It is important not to inhale dust of lead
carbonate or the oxide formed.
-Wash hands before leaving the lab
Conclusions:
Metals high up in the reactivity series -
such as potassium- have carbonates that need a lot of energy to decompose them.
Metals low down in the reactivity series - such as copper - have carbonates
that are easily decomposed. Hence, the more reactive the metal is, the more
difficult it is to decompose its compounds.
Credits:
