Ammonia is commonly produced from ammonium salts by reacting them with a strong base, often involving heating.
Producing Ammonia from Ammonium Chloride in a Laboratory
One method to generate ammonia gas, particularly in a laboratory setting, involves a specific reaction as described in the reference:
- Reactants: Ammonium chloride ($\text{NH}_4\text{Cl}$) and slaked lime [$\text{Ca(OH)}_2$].
- Process: The mixture of ammonium chloride and slaked lime is slowly heated.
- Outcome: This reaction produces ammonia gas ($\text{NH}_3$).
Slaked lime, calcium hydroxide ($\text{Ca(OH)}_2$), is used because it is a base. When an ammonium salt reacts with a strong base upon heating, it releases ammonia gas, water, and a salt.
The chemical reaction can be represented as:
$2\text{NH}_4\text{Cl}\text{(s)} + \text{Ca(OH)}_2\text{(s)} \rightarrow \text{CaCl}_2\text{(s)} + 2\text{H}_2\text{O}\text{(g)} + 2\text{NH}_3\text{(g)}$
This equation shows that solid ammonium chloride reacts with solid calcium hydroxide (slaked lime) upon heating to produce solid calcium chloride, water vapor, and ammonia gas.
Why Use This Method?
- Availability: Ammonium chloride and slaked lime are readily available chemicals.
- Simplicity: The process involves simple mixing and heating.
- Effectiveness: It's an effective laboratory method for generating relatively small quantities of ammonia gas.
Collecting the Ammonia Gas
Once produced, the ammonia gas needs to be collected. The reference notes a specific collection method:
- Method: Accumulation by the descending displacement of air.
- Reason: Ammonia gas is lighter than air.
This means that as the ammonia gas is produced, it is directed into a collection vessel (like a gas jar). Since it is lighter than air, it rises to the top of the vessel, pushing the heavier air downwards and out. This method ensures that the relatively light ammonia gas is efficiently captured.
Summary of the Process
| Feature | Description |
|---|---|
| Reactants | Ammonium Chloride ($\text{NH}_4\text{Cl}$), Slaked Lime [$\text{Ca(OH)}_2$] |
| Process | Slow Heating |
| Products | Ammonia ($\text{NH}_3$), Calcium Chloride ($\text{CaCl}_2$), Water ($\text{H}_2\text{O}$) |
| Collection Method | Descending Displacement of Air |
In summary, ammonia gas is effectively produced from ammonium chloride in a laboratory setting by slowly heating it with slaked lime, utilizing the reaction between an ammonium salt and a base. The resulting ammonia, being lighter than air, is then collected using the descending displacement of air method.
