1. Acid-Base Reaction:
* Alka-Seltzer contains sodium bicarbonate (NaHCO₃), a base, and citric acid (C₆H₈O₇), an acid.
* When these ingredients dissolve in water, they react to form sodium citrate (Na₃C₆H₅O₇), water (H₂O), and carbon dioxide (CO₂) gas.
* This reaction releases heat, making the solution warmer.
2. Dissolution of Salts:
* The reaction produces sodium citrate, a salt that dissolves in water.
* The dissolution of salts in water is usually an exothermic process, contributing to the heat release.
3. Gas Evolution:
* The reaction produces carbon dioxide gas, which bubbles up and escapes from the solution.
* The energy required to break the bonds in the reactants is less than the energy released when new bonds form in the products. This difference in energy is released as heat.
Overall:
The combination of the acid-base reaction, salt dissolution, and gas evolution results in the release of a significant amount of heat, making Alka-Seltzer an exothermic reaction. This is why you feel the tablet fizzing and the solution warming up when it dissolves in water.
