Student s Name: Date : Preparation and properties of ammonia - NH 3 (g)

Transcription

1 Student s Name: Date : Background Preparation and properties of ammonia - NH 3 (g) Ammonia is used as a cleaning agent in household ammonia solution, as a cheap base in industry, in the manufacture of fertilizers, dyes and explosives. In this experiment the preparation and properties of ammonia will be investigated. Equipment and chemicals 250 ml conical flask with flexible ammonium chloride NH 4 Cl - 4g gas delivery tube fitted into a rubber stopper 3 large test tubes with stoppers calcium hydroxide Ca(OH) 2-3 g 1 medium test tube (to test a solution) stirring rod test tube rack hot plate retort stand and clamp (to stabilize the reaction flask) concentrated HCl bottle (test fumes) R.O. water wash bottle universal indicator red and blue litmus paper wax taper (or wooden splint) Safety Ammonia has an irritating-choking odour. Avoid inhaling the ammonia gas. Prepare and test ammonia gas in the fume cupboard. Concentrated hydrochloric acid is very corrosive ad must be handled with care. If any concentrated hydrochloric acid comes into contact with your skin or eyes, immediately wash the affected area with copious quantities of water. Ask for help. International safety card information hydrochloric acid - ammonium chloride - calcium hydroxide - ammonia - harmful NH 4 Cl HCl NH 3, HCl HCl, NH 3 STAWA20.DOC Adapted from STAWA Exp 20 Page 1

2 Procedure Gas production 1. Set up the gas generating equipment to collect the ammonia by the downward displacement of air as shown in the diagram below. ammonia gas a few drops of RO water air displaced downwards by ammonia gas ammonium chloride + calcium hydroxide low heat hot plate 2. Clamp the reaction flask (to prevent accidental spillage) 3. Place about 4 g of ammonium chloride NH 4 Cl and 3 g of calcium hydroxide Ca(OH) 2. Add a few drops of RO water, but not to much. Mix the damp powder with a stirring rod. Replace the gas collection stopper and tubing. 4. Use a hotplate to gently heat the reaction flask. Collect three test tubes of ammonia gas. You can tell when the test tube is full by holding a piece of moist red litmus paper at the mouth. It turns blue when the test tube is full. Stopper each test tube and place in a test tube rack. STAWA20.DOC Adapted from STAWA Exp 20 Page 2

3 Gas testing 5. Hold the stopper from a bottle of concentrated HCl near the gas delivery tube and record your observations. 6. Half fill a test tube with RO water and add 3 drops of universal indicator. Bubble some ammonia gas through the solution and not the colour change. 7. After the reaction flask has cooled down, carefully wash it out with plenty of water. 8. Use the first test tube of ammonia to observe its colour and carefully detect its odour. 9. Into the second test tube, place a lighted wax taper (or wooden splint). 10. Remove the stopper from the third test tube, quickly add 1 ml of water and replace the stopper. Shake the test tube, remove the stopper and add small pieces of red and blue litmus paper. Record your observations. 11. Safely dispose of all spent chemicals and clean the work area for the next group. Data Sheet NH 3 - Ammonia gas observations colour odour universal indicator litmus paper burning wax taper test HCl (g) + NH 3 (g) STAWA20.DOC Adapted from STAWA Exp 20 Page 3

4 Processing of Results 1. Write a balanced equation for the preparation of ammonia. 2. List the following physical properties of ammonia colour odour density solubility in water acidic or alkaline property 3. From your observations, what can you say about the solubility of ammonia in water? Write an equation to show the reaction that takes place when ammonia dissolves in water. Does this account for the colour of the universal indicator and the litmus paper? STAWA20.DOC Adapted from STAWA Exp 20 Page 4

5 4. Could ammonia gas be collected using the downward displacement of water method? Explain. 5. Write an equation for the reaction between ammonia and hydrogen chloride. 6. Does ammonia support combustion? STAWA20.DOC Adapted from STAWA Exp 20 Page 5