When Alka-Seltzer is added to water, it undergoes a chemical reaction that produces carbon dioxide gas. The primary ingredients in Alka-Seltzer are sodium bicarbonate (baking soda) and citric acid.
The reaction can be summarized as follows:
Chemical Equation:
NaHCO₃ (s) + C₆H₈O₇ (s) + H₂O (l) → NaC₆H₅O₇ (aq) + H₂CO₃ (aq) → NaC₆H₅O₇ (aq) + CO₂ (g) + H₂O (l)In this reaction:
- Sodium bicarbonate (NaHCO₃) reacts with citric acid (C₆H₈O₇) when dissolved in water.
- The immediate products are sodium citrate (NaC₆H₅O₇) and carbonic acid (H₂CO₃).
- Carbonic acid then decomposes into water and carbon dioxide gas (CO₂), which is what causes the fizzing effect.
This fizzing you observe is the release of carbon dioxide gas, which is responsible for the effervescence you see in the solution. This reaction is also why Alka-Seltzer is effective in relieving indigestion and discomfort, as the gas helps to move things along in the digestive system.