MYP 3 Experiment 2.3 An experiment to follow the rate of reaction between hydrochloric acid and calcium carbonate Introduction Hydrochloric acid (HCl) and calcium carbonate (CaCO3) react to produce calcium chloride (CaCl2), which is a water-soluble salt, carbon dioxide gas and water. There are various ways of following rates of reaction. In this case, you will measure the volume of gas evolved with time. The more gas evolved per second, the greater the rate. You will plot a graph of this data, and use it to see how the rate changes during the reaction. Instructions • Set up the apparatus as shown by your teacher. • Drop 3 marble chips into 50cm3 of hydrochloric acid (1mol.dm-3 concentration), and quickly insert the bung. • Simultaneously, start a stop-clock. Record the volume of gas evolved at suitable time intervals. At first, this should be every 10 seconds. You may find you want to increase the time intervals as the reaction proceeds. • Remove the bung as soon as the volume of gas evolved reaches 100 cm³. • Record your results in a suitable table.