The Chemistry:
* Sodium hydroxide is hygroscopic: This means it readily absorbs moisture from the air.
* Carbon dioxide in the air: The atmosphere contains carbon dioxide.
* Reaction: When sodium hydroxide absorbs moisture, it forms an aqueous solution. This solution then reacts with carbon dioxide to form sodium carbonate and water:
2NaOH (aq) + CO2 (g) → Na2CO3 (aq) + H2O (l)
Consequences of Carbonate Contamination:
* Reduced purity: The presence of sodium carbonate lowers the purity of the sodium hydroxide.
* Impacted reactions: The presence of carbonate ions can interfere with chemical reactions, leading to unexpected results or side reactions.
* pH changes: Sodium carbonate is basic, but less so than sodium hydroxide. This can affect the pH of solutions and influence reactions.
Minimizing Contamination:
* Storage: Sodium hydroxide should be stored in airtight containers to minimize exposure to moisture and carbon dioxide.
* Handling: Handling sodium hydroxide in a dry, well-ventilated area can help reduce contamination.
* Preparation: Solutions of sodium hydroxide can be prepared using freshly boiled, cooled water to remove dissolved carbon dioxide.
In summary, the contamination of sodium hydroxide with sodium carbonate is a result of its reaction with carbon dioxide in the atmosphere due to its hygroscopic nature. This can affect the purity and reactivity of sodium hydroxide, making it crucial to consider and minimize this contamination.
