Question

How is ammonia gas prepared in laboratory?

Short answer

Answer: To prepare ammonia gas in the laboratory, the primary materials required are ammonium chloride (NH4Cl) and a strong alkali such as calcium hydroxide (Ca(OH)2). The production of ammonia gas (NH3) occurs through a double displacement reaction, represented by the balanced chemical equation: NH4Cl + Ca(OH)2 -> NH3 (g) + H2O + CaCl2(s).

Step-by-step solution

Gather materials required

The materials required for this experiment are as follows: 1. Ammonium chloride (NH4Cl) 2. Calcium hydroxide (Ca(OH)2) 3. A round-bottom flask 4. A glass delivery tube 5. A gas collection vessel (a gas jar or container filled with water) 6. Ice bath 7. Retort stand, clamp and boss 8. Rubber bungs and tubing 9. Protective gloves, goggles, and a lab coat

Set up the apparatus

Place the round-bottom flask on a retort stand, securing it with a clamp and boss. Attach the glass delivery tube (bent at an angle) to the flask using a rubber bung. Prepare the ice bath to cool the ammonia gas, as it is highly soluble in water.

Mix the reactants

Weigh out the appropriate amounts of ammonium chloride (NH4Cl) and calcium hydroxide (Ca(OH)2), typically in a 1:1 molar ratio, since the balanced chemical equation for the reaction is: NH4Cl + Ca(OH)2 -> NH3 (g) + H2O + CaCl2(s) Add both reactants to the flask and mix them gently.

Heat the mixture

Gently heat the mixture using a Bunsen burner or hot water bath. The reactants will undergo a double displacement reaction to form ammonia gas (NH3), water (H2O), and calcium chloride (CaCl2).

Collect the ammonia gas

The ammonia gas will travel up the delivery tube and into the ice bath, which will cool it. It is essential to cool the gas, as ammonia is highly soluble in water. Fill the gas collection vessel with water and invert it over the end of the delivery tube. The ammonia gas will then displace the water in the vessel.

Observe safety precautions

Ensure proper ventilation in the lab, as ammonia gas is toxic and can irritate the respiratory system. Wear protective gloves, goggles, and a lab coat at all times during the experiment.

Clean up and dispose of chemicals

Once the desired amount of ammonia gas is collected, turn off the heat and allow the flask to cool. Dispose of the calcium chloride and unreacted chemicals according to your lab's waste disposal guidelines. Clean and store the apparatus appropriately.