Thermal decomposition of carbonates

Watch the following video which shows the effect of heating the Group 2 carbonates from magnesium carbonate to barium carbonate. These thermal decomposition reactions produce carbon dioxide gas. I have shown a fairly simple experiment in which any gases are passed through lime-water to detect any carbon dioxide gas. The principle behind this experiment is to see if there is any trend in the ease of decomposition of these carbonates as we go down the group.

Limewater goes cloudy in the presence of carbon dioxide

In each case I have used 0.025 moles of the carbonate, and heated it with the same Bunsen burner on the same setting and at the same position. Make a note of the time taken for the cloudiness of the lime-water to first appear. This is a rough measure of the ease of decomposition - the shorter it takes the less stable is the carbonate. Also the degree of cloudiness gives an indication of the stability. More cloudiness means more carbon dioxide and so quicker decomposition.

Write equations for the reactions and try to explain any trend that you observe. Suggest how stable group 1 carbonates are towards heat. Check your answers here.

Video - thermal decomposition of group 2 carbonates