What Are Metal Hydrogen Carbonates?
Metal hydrogen carbonates, commonly known as bicarbonates, have the general formula MHCO₃, where M is a metal like sodium (NaHCO₃, baking soda) or potassium (KHCO₃).
Reaction With Acids
When an acid reacts with a metal hydrogen carbonate, the products are:
- A salt
- Carbon dioxide gas (CO₂)
- Water (H₂O)
General reaction:
Acid + Metal hydrogen carbonate → Salt + CO₂ + H₂O
Example:
HCl(aq) + NaHCO₃(s) → NaCl(aq) + CO₂(g) + H₂O(l)
Example:
HCl(aq) + NaHCO₃(s) → NaCl(aq) + CO₂(g) + H₂O(l)
Explanation
The acid reacts with the bicarbonate ion (HCO₃⁻). The reaction releases carbon dioxide gas, which is observed as bubbling or fizzing.
Visual Representation
Fizzing shows CO₂ gas being released (Image via chemistrytalk.org)
Real-life Applications
- Baking: Baking powders contain sodium bicarbonate. They react with acids in the recipe to help cakes rise by releasing CO₂.
- Fire extinguishers: Some fire extinguishers use sodium bicarbonate, which reacts with acid to produce CO₂, smothering fires.
- Antacids: Effervescent antacid tablets often use this reaction to neutralize excess stomach acid and release CO₂ bubbles.
Key Points to Remember
- Bicarbonates react with acids to produce a salt, carbon dioxide, and water.
- The reaction is often accompanied by fizzing — the visible sign of CO₂ gas.
- This is a classic example of an acid-carbonate reaction in chemistry.