Chemistry for 14 -16 year olds: Calcium Carbonate Cycle

Description
One of several hundred video-tuitions in high school chemistry, available at www.20to9.com We start with limestone, heating it strongly for 1 hour. The quicklime formed is reacted (slaked) with cold water to form slaked lime (LIME). This is calcium hydroxide. A suspension of this in water is filtered giving a very dilute solution of the hydroxide as the filtrate. This is limewater. Carbon dioxide is bubbled through the limewater until it goes cloudy and then clear again. Insoluble calcium carbonate and then soluble calcium hydrogen carbonate are formed in turn. The hydrogen carbonate solution is warmed and goes cloudy, due to thermal decomposition back into calcium carbonate.