Properties and Reactions of Acids and Carbonates

Fundamental Acid-Carbonate Reactions

• Definition: A reaction occurring when an acid reacts with a carbonate or hydrogen carbonate (bicarbonate).

• The Carbonate Ion: Carbonates are identified by the $CO_3^{2-}$ ion (e.g., $Na_2CO_3$, $CaCO_3$).

• General Word Equation: $\text{Acid} + \text{Carbonate} \rightarrow \text{Salt} + \text{Water} + \text{Carbon dioxide}$

Chemical Examples

• Hydrochloric acid + sodium carbonate: $HCl + Na_2CO_3 \rightarrow 2NaCl + CO_2 + H_2O$

• Sulfuric acid + calcium carbonate: $H_2SO_4 + CaCO_3 \rightarrow CaSO_4 + CO_2 + H_2O$

• Hydrochloric acid + calcium carbonate: $HCl + CaCO_3 \rightarrow CaCl_2 + H_2O + CO_2$

The Lime-water Test for Carbon Dioxide

• Process: Carbon dioxide is bubbled through lime water, which is aqueous calcium hydroxide ($Ca(OH)_2$).

• Result: A precipitate of calcium carbonate ($CaCO_3$) forms, causing the solution to appear cloudy.

• Equation: $Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O$

Observable Evidence of Reaction

• Gas Production: Fizzing or bubbling indicates the release of $CO_2$ gas.

• Physical Changes: The solid carbonate may dissolve as the reaction proceeds.

• Thermal Property: These are exothermic reactions resulting in a temperature change.

• Product Formation: Creation of a new salt based on the specific acid and carbonate reactants.