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How to Test the Solubility of Ammonia Gas

The chemical reference materials, such as the CRC Handbook of Chemistry and Physics, claim that the solubility of ammonia gas in water is high -- 8 cubic centimeters of ammonia can dissolve into one milliliter of water. Demonstrating this fact is possible by executing a simple experiment. By generating ammonia gas in a test tube and filling a second test tube with the ammonia, the ammonia gas begins to dissolve into the water when you turn the tube upside down under the surface of a beaker of water. The level of water rises in the test tube as the ammonia dissolves into the water.

Things You'll Need

Goggles
100 ml beaker
Ammonium chloride
Spatula
Calcium hydroxide
Ring stand
Clamp
Boiling tubes
Stopper and delivery tube
Bunsen burner
Calcium oxide
250 ml beaker

Instructions

Preparation of Equipment
- 1
  Place all the items to be used in the fume hood to protect you and others from the fumes created during the reaction.
- 2
  Assemble a ring stand with a clamp rotated to hold a test tube horizontally. Fill the 250 ml beaker with 150 milliliters of water.
- 3
  Place a stopper and delivery tube into a boiling tube with the delivery tube pointed upwards.
Experiment
- 4
  Transfer two spatulas full of ammonium chloride -- approximately 1 gram -- into a 100 ml beaker. Add two spatulas full of calcium hydroxide to the beaker and stir. As the chemicals mix, they will react immediately.
- 5
  Remove the stopper and delivery tube from the boiling tube and transfer the contents of the 100 ml beaker into the boiling tube. Place a lump of calcium oxide in the mouth of the boiling tube and replace the stopper. The calcium oxide will absorb any water produced in the reaction between the ammonium chloride and calcium hydroxide.
- 6
  Clamp the boiling tube horizontally to the ring stand and move the Bunsen burner below the closed end of the tube.
- 7
  Light the Bunsen burner and gently warm the reaction mixture. This will help complete the reaction described by this equation, 2 NH4Cl(s) + Ca(OH)2(s) --> CaCl2(s) + NH3(g) + 2 H2O(g), where the s and g represent the states of the chemicals in question as solid or gas.
- 8
  Invert a boiling tube over the top of the upturned delivery tube and allow sufficient time for the ammonia to fill the tube.
- 9
  Remove the boiling tube filled with ammonia from the outlet of the delivery tube and place it in the 250 ml beaker, carefully placing the open end under the surface of the water. Allow at least 1 inch of space between the surface of the water and the opening of the boiling tube.
- 10
  Observe the level of the water rising in the boiling tube. The water level rises due to the reduction of ammonia gas in the tube above the water. The ammonia dissolves in the water, reducing the pressure of the gas in the tube and draws the water up further.

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