How to Prepare an Ammonia Solution Using Ammonium Chloride: Steps and Safety Guidelines

How is an Ammonia Solution Prepared from Ammonium Chloride?

An ammonia solution is prepared by adding a strong base, typically concentrated sodium hydroxide (NaOH), to ammonium chloride (NH4Cl). This causes the release of ammonia gas (NH3), which is then bubbled through distilled water to dissolve, forming the ammonia solution.

Chemical Principle Behind the Reaction

Ammonium chloride contains ammonium ions (NH4+), not free ammonia. To obtain ammonia gas, the ammonium ions must be converted to NH3 by reacting with hydroxide ions (OH-) from a strong base. The overall reaction is:

NH4Cl (s) + NaOH (aq) → NH3 (g) + NaCl (aq) + H2O (l)

This reaction liberates ammonia gas while producing sodium chloride and water.

Reagents and Conditions

• Strong Base: Use concentrated sodium hydroxide (~50%) to drive the reaction efficiently.
• Minimal Water: Limit water content in the reaction flask to reduce ammonia dissolution at the source, ensuring more gas escapes.

Experimental Setup and Procedure

1. Place solid ammonium chloride in a reaction flask.

2. Slowly add concentrated NaOH to the flask.

3. Ammonia gas forms as a product and exits the reaction vessel through tubing.

The ammonia gas is directed into a separate container holding distilled water. Bubbling ammonia gas into this water produces aqueous ammonia (ammonia solution).

To prevent water from flowing back into the reaction flask — which can happen due to rapid ammonia absorption — keep the tube end just above the water surface or use an inverted funnel slightly above the water. This setup is similar to an “ammonia fountain.”

Safety Considerations

• Sodium Hydroxide: Highly corrosive; wear gloves and goggles. Rinse immediately if contacted by skin.
• Ammonia Gas: Has a strong odor that irritates the eyes and respiratory tract. Work in a well-ventilated area.

Important Details

• Use distilled water to ensure purity of the ammonia solution.
• Add NaOH slowly to control reaction rate and gas evolution.
• Design apparatus to avoid water back-suction into the reaction flask.

Key Takeaways

• Ammonium chloride is converted to ammonia gas by reaction with concentrated sodium hydroxide.
• Minimal water is maintained in the reaction flask to maximize gas yield.
• Ammonia gas is bubbled into distilled water to form an aqueous ammonia solution.
• Proper apparatus setup prevents backflow of water and loss of ammonia.
• Strict safety measures are essential when handling corrosive NaOH and irritating ammonia gas.

How is ammonia gas liberated from ammonium chloride?

Ammonia gas is released by adding concentrated sodium hydroxide to ammonium chloride. The base converts the ammonium ion into ammonia gas, which can then be collected.

Why should the reaction mixture contain minimal water?

Minimizing water reduces ammonia’s immediate dissolution. Less water helps ammonia gas escape more effectively before it dissolves.

How is ammonia gas collected to form an ammonia solution?

The ammonia gas is bubbled through distilled water in a separate container. This dissolves the gas, yielding an aqueous ammonia solution.

What equipment precautions prevent water from flowing back into the reaction flask?

An inverted funnel just above the water surface is used. This prevents rapid ammonia absorption that would suck water back into the reaction vessel.

What safety measures are necessary during the preparation?

Wear goggles and gloves when handling sodium hydroxide. Keep water nearby to rinse off any spills. Ammonia gas is irritating, so work in a ventilated area.