The kitchen salt
Baking soda is a mild basic salt that breaks up when heated.
Bubbles in the pakora batter
When a cook heats a batter with baking soda, it puffs up. Something is escaping as a gas.
Which gas could it be?
What this lesson covers
The idea
Baking soda is sodium hydrogencarbonate (NaHCO3), a mild non-corrosive basic salt made using sodium chloride; on heating it decomposes into sodium carbonate, water and carbon dioxide.
Bubbles in the pakora batter
When a cook heats a batter with baking soda, it puffs up. Something is escaping as a gas.
Which gas could it be?
- Carbon dioxide
- Chlorine
- Hydrogen
Test it, then heat it
First, is baking soda acidic or basic? Dip each indicator in each solution.
Now heat dry baking soda and pass the gas into lime water.
Baking soda breaks up when heated
Baking soda is sodium hydrogencarbonate, NaHCO₃, a mild, non-corrosive basic salt made using sodium chloride. On heating it decomposes into sodium carbonate, water and carbon dioxide.
How it is made: NaCl + H₂O + CO₂ + NH₃ → NH₄Cl + NaHCO₃.
- Before heating | After heating
- 2NaHCO₃ (baking soda) | Na₂CO₃ + H₂O + CO₂
Notes
Baking soda is sodium hydrogencarbonate (NaHCO₃), a mild non-corrosive basic salt made using sodium chloride; on heating it decomposes into sodium carbonate, water and carbon dioxide.
Check yourself
What is the chemical name of baking soda?
Baking soda solution turns red litmus blue. So it is …
Heated baking soda gives a gas that turns lime water milky. The gas is …
Which are the products when baking soda is heated?
- Sodium hydroxide. That is NaOH, a strong base.
- Sodium chloride. That is common salt, NaCl.
- Sodium hydrogencarbonate — correct. Yes! NaHCO₃.
- basic (a mild base) — correct. Yes! A mild, non-corrosive basic salt.
- acidic. Acids do not turn red litmus blue.
- neutral. It changed the litmus, so it is not neutral.
- hydrogen. Hydrogen does not turn lime water milky.
- carbon dioxide — correct. Yes! The lime-water test.
- oxygen. Oxygen does not turn lime water milky.
- Sodium chloride and hydrogen. Sodium chloride is not formed on heating baking soda.
- Sodium hydroxide and oxygen. These are not the products. It breaks into Na₂CO₃, H₂O and CO₂.
- Sodium carbonate, water and carbon dioxide — correct. Yes!