Final answer:
To check if a chemical reaction has occurred when combining calcium carbonate with acids, look for evidence like gas production, temperature changes, color changes, or precipitate formation. Carbon dioxide production, often visible as bubbles, is a key indicator for reactions with acids.
Step-by-step explanation:
To determine whether a chemical reaction has occurred when combining calcium carbonate with substances like malic acid, sulfuric acid, nitric acid, or water, you would look for evidence such as a change in temperature, the production of gas, a color change, or the formation of a precipitate. When calcium carbonate reacts with an acid like sulfuric or nitric acid, it forms carbon dioxide gas and water, along with a salt of the respective acid:
- CaCO3(s) + H2SO4(aq) → CaSO4(aq) + CO2(g) + H2O(l)
- CaCO3(s) + 2HNO3(aq) → Ca(NO3)2(aq) + CO2(g) + H2O(l)
The most reliable evidence of a reaction in these cases is the formation of bubbles or fizzing, indicating the release of carbon dioxide gas. A change in temperature may also occur, suggesting an exothermic reaction. If carbon dioxide gas is produced, passing the gas through limewater can provide further evidence of the reaction, as the limewater will turn milky due to the formation of calcium carbonate from the reaction between CO2 and the calcium hydroxide in the limewater.
With water, no visible reaction occurs because calcium carbonate is only slightly soluble in water and does not react with it under normal conditions.