Yes, ammonia gas is very soluble in water.
Ammonia ($\text{NH}_3$) is known for its high solubility in water ($\text{H}_2\text{O}$). When ammonia gas dissolves in water, it forms an aqueous solution commonly known as ammonia water or ammonium hydroxide.
Why is Ammonia So Soluble in Water?
The primary reason behind the high solubility of ammonia in water is the formation of hydrogen bonds.
- Hydrogen Bonding: Water molecules are polar, with partial positive charges on the hydrogen atoms and a partial negative charge on the oxygen atom. Ammonia molecules are also polar, with a partial negative charge on the nitrogen atom and partial positive charges on the hydrogen atoms. These opposing partial charges allow hydrogen bonds to form between the hydrogen atoms of water and the nitrogen atom of ammonia, and also between the hydrogen atoms of ammonia and the oxygen atom of water.
- Strong Interaction: Hydrogen bonds represent a relatively strong intermolecular force. The ability of ammonia and water molecules to form these extensive hydrogen bond networks allows the two substances to mix readily and stay dissolved.
The reference explicitly states that ammonia gas is very soluble in water, attributing this high solubility directly to the hydrogen bonding that occurs between ammonia and water molecules.
What Happens When Ammonia Dissolves?
While ammonia dissolves readily due to hydrogen bonding, a small portion of the dissolved ammonia also reacts with water to form ammonium ions ($\text{NH}_4^+$) and hydroxide ions ($\text{OH}^-$):
$\text{NH}_3\text{(aq)} + \text{H}_2\text{O(l)} \rightleftharpoons \text{NH}_4^+\text{(aq)} + \text{OH}^-\text{(aq)}$
This equilibrium reaction makes ammonia solutions basic (alkaline). However, the vast majority of dissolved ammonia exists as $\text{NH}_3$ molecules surrounded by water molecules via hydrogen bonds.
Solubility Comparison
Compared to many other gases, ammonia's solubility in water is exceptionally high. For example:
| Gas | Solubility in Water (at 20°C, 1 atm) |
|---|---|
| Ammonia | ~700 liters per liter of water |
| Oxygen | ~31 milliliters per liter of water |
| Nitrogen | ~19 milliliters per liter of water |
| Carbon Dioxide | ~1.7 liters per liter of water |
Note: Solubility varies significantly with temperature and pressure.
This table clearly illustrates that ammonia is far more soluble than common gases like oxygen, nitrogen, or even carbon dioxide.
Practical Implications
The high solubility of ammonia in water has several practical applications:
- Household Cleaning Products: Ammonia water is a common cleaning agent.
- Industrial Processes: Used in the production of fertilizers, plastics, and pharmaceuticals.
- Refrigeration: Ammonia was historically used as a refrigerant (though less common now in many domestic applications).
In summary, ammonia gas dissolves extensively in water primarily because of the strong attractive forces created by hydrogen bonding between the $\text{NH}_3$ and $\text{H}_2\text{O}$ molecules.
