Contrary to the question's premise, sodium oxide (Na₂O) is not soluble in water. Instead of simply dissolving, it undergoes a vigorous chemical reaction when it comes into contact with water.
What Happens When Sodium Oxide Meets Water?
When sodium oxide is exposed to water, a chemical reaction takes place. This reaction is characterized by its intensity and the formation of new substances.
As stated in the provided reference from January 17, 2021: "sodium oxide is not soluble in water. Na2O reacts violently when exposed to water, forming sodium hydroxide in the process."
The reaction can be represented by the following equation:
Na₂O (s) + H₂O (l) → 2NaOH (aq)
In this reaction:
- Sodium oxide (Na₂O), a solid, reacts with
- Water (H₂O), a liquid, to produce
- Sodium hydroxide (NaOH), which dissolves in the water (indicated by (aq) for aqueous solution).
This is a type of acid-base reaction, where a basic oxide (sodium oxide) reacts with water to form a base (sodium hydroxide). The reaction is highly exothermic, meaning it releases a significant amount of heat, contributing to its violent nature.
Reaction vs. Dissolution: A Key Distinction
It's important to understand the difference between a substance dissolving and a substance reacting with the solvent.
- Dissolving (Solubility): A physical process where a substance disperses evenly throughout a solvent, forming a solution. The original substance is still present, just in a dispersed form.
- Reacting: A chemical process where the original substance changes into new substances. Chemical bonds are broken and formed.
Sodium oxide does not dissolve; it is chemically transformed into sodium hydroxide.
Comparing Processes
| Aspect | Dissolving (Solubility) | Reacting (Chemical Change) |
|---|---|---|
| Process Type | Physical | Chemical |
| Original Substance | Remains, dispersed | Transformed into new substance(s) |
| Energy Change | Can be endothermic or exothermic | Often exothermic (as with Na₂O/H₂O) |
| Na₂O + Water | Does NOT dissolve | REACTS violently to form NaOH |
Implications and Safety
The violent reaction of sodium oxide with water and the resulting product have practical implications:
- Formation of Sodium Hydroxide: The product, sodium hydroxide (NaOH), is a strong base. Solutions of sodium hydroxide are highly corrosive and can cause severe burns upon contact with skin, eyes, or other tissues.
- Safety Hazard: The reaction's violence and heat release, combined with the corrosive nature of the product, make handling sodium oxide and its contact with water a significant safety hazard.
- Storage: Due to its reactivity with moisture, sodium oxide must be stored in a sealed container in a very dry environment to prevent accidental reaction with atmospheric water vapor or liquid water.
In summary, sodium oxide is not soluble in water because it undergoes a complete chemical transformation into sodium hydroxide upon contact, rather than simply dispersing within the water.
