A student dropped few pieces of marble in dilute HCl contained in a test tube. The gas evolved was passed through lime water. What change would be observed in lime water ? Write the chemical equation for both the changes observed.
Marble is chemically calcium carbonate. When dilute HCl is added to calcium carbonate, it forms calcium chloride, water and carbon dioxide. The chemical equation for the reaction is as follows
CaCO3 + 2HCl → CaCl2 + H2O + CO2
Carbon dioxide gas turns lime water milky due to the formation of calcium carbonate. Following is the chemical equation showing the reaction between lime water and carbon dioxide.
Ca(OH)2 + CO2 → CaCO3 + H2O