4️⃣PAG 5 Identification of species Flashcards
Safety - general
Safety
Wear splash proof eye protection throughout.
Do not touch any of the chemicals or solutions as some may be harmful or toxic and others may be corrosive. If you do accidentally touch a chemical, rinse the affected area immediately with water.
SAFETY identifying positive ions
Safety
• 0.4 mol/dm3 sodium hydroxide: IRRITANT
• 0.4 mol/dm3 calcium chloride: IRRITANT
• 0.4 mol/dm3 zinc nitrate solution: IRRITANT
• 0.4 mol/dm3 iron(III) chloride solution: CORROSIVE
• 0.4 mol/dm3 copper(II) sulfate solution: CORROSIVE
• 0.4 mol/dm3 iron(II) sulfate (or iron(II) chloride solution, see note below): CORROSIVE
• Wear chemical splash proof eye protection
Equipment sodium hydroxide test
- 0.4 mol/dm3 calcium chloride solution
- 0.4 mol/dm3 zinc nitrate solution
- 0.4 mol/dm3 iron(III) chloride solution
- 0.4 mol/dm3 copper(II) sulfate solution
- 0.4 mol/dm3 iron(II) sulfate solution
- 0.4 mol/dm3 sodium hydroxide
- spotting tile
- droppers
Setting the scene - positive ion tests
Two types of tests can be used to identify which positive ion (or _ion) is present in a solution – the __ __ test and the __ test.
The sodium hydroxide test relies on the fact that different metal ions produce different coloured __ when sodium hydroxide is added to a solution containing the metal ion. You will be carrying out the sodium hydroxide test on some solutions.
The flame test relies on the fact that different metal ions produce different colours of __ when heated in a hot Bunsen burner flame. You will observe a demonstration of the flame test on some solutions with unknown positive ions.
Setting the scene
Two types of tests can be used to identify which positive ion (or cation) is present in a solution – the sodium hydroxide test and the flame test.
The sodium hydroxide test relies on the fact that different metal ions produce different coloured precipitates when sodium hydroxide is added to a solution containing the metal ion. You will be carrying out the sodium hydroxide test on some solutions.
The flame test relies on the fact that different metal ions produce different colours of light when heated in a hot Bunsen burner flame. You will observe a demonstration of the flame test on some solutions with unknown positive ions.
Sodium hydroxide test - method - 4
Sodium hydroxide test
1 Using a separate dimple for each solution place two drops of each solution to be tested (calcium chloride, zinc nitrate, iron(II) sulfate, iron(III) chloride, and copper(II) sulfate) onto a spotting tile.
2 To each solution in turn, add sodium hydroxide solution dropwise until in excess.
3 Note the colour of each precipitate and whether it dissolves in excess sodium hydroxide.
4 Record your observations in the results table below.
Flame test method - 6
1 Use a spatula to put a small amount of the first test substance on a watch glass.
2 Dip the nichrome wire in the concentrated hydrochloric acid and the tip in a blue Bunsen flame. Repeat until no colour is seen.
3 Dip the wire into the first powder and then hold the tip of the wire in a blue Bunsen burner flame.
4 Record the colour of the flame in the table below.
5 Clean the wire carefully between tests by dipping it into the concentrated hydrochloric acid and holding it in the hot flame until no more colour is visible.
6 Test the other four solids in the same way and record your observations in the results table.
Making and testing gasses safety
• eye protection • zinc granules: LOW HAZARD • 2 mol/dm3 hydrochloric acid: IRRITANT • limewater: IRRITANT • hydrogen peroxide: OXIDISER, IRRITANT • manganese dioxide: HARMFUL • chlorine water: HARMFUL – avoid fumes especially if you are asthmatic
Equipment making/testing gasses
• three test tubes • test tube rack • three conical flasks with delivery tubes • three bungs • 25 cm3 measuring cylinder • water trough • limewater • zinc granules • 2 mol/dm3 hydrochloric acid • marble chips • hydrogen peroxide • manganese dioxide • spatula • splints Teacher demonstration: • chlorine water • blue litmus paper
Method - making and testing for carbon dioxide
Making and testing for carbon dioxide
1 Half-fill a test tube with limewater and place in a test tube rack.
2 Put the end of a delivery tube into the limewater.
3 Add about 25 cm3 of hydrochloric acid to a conical flask and add a few marble chips.
4 Quickly put a bung on the conical flask and observe the limewater.
Method - making and testing for hydrogen
Making and testing for hydrogen
1 Half fill the trough with water.
2 Fill the test tube with water and leave it full of water in the trough.
3 Add about 100 cm3 of hydrochloric acid into the conical flask and add one spatula measure of zinc granules.
4 Put the bung on the conical flask and put the end of the delivery tube in the trough.
5 Wait about a minute to ensure the air has been removed from the system.
6 Collect the gas in the test tube.
7 When it is full of gas, put a bung on the test tube while the lip is still under the water.
8 Test the gas by removing the bung and holding a lighted splint at the neck of the test tube.
Method - making and testing for oxygen
Making and testing for oxygen
1 Half fill the trough with water.
2 Fill the test tube with water and leave it full of water in the trough.
3 Add about 25 cm3 hydrogen peroxide to a conical flask with one spatula measure of manganese dioxide.
4 Put the bung on the conical flask and put the end of the delivery tube in the water trough.
5 Wait about a minute to ensure the air has been removed from the system.
6 Collect the gas in the test tube.
7 Light a splint and gently blow or tap it so that it is only glowing.
8 Hold the glowing splint in the test tube and observe.
Test for chlorine
Test for chlorine (teacher demonstration)
1 Use a drop of tap water to dampen a piece of blue litmus paper.
2 Hold the paper near to a sample of chlorine water and observe what happens to the litmus paper
Safety - tests for anions
Safety
• Wear eye protection
• 0.4 mol/dm3 dilute hydrochloric acid: LOW RISK
• 0.1 mol/dm3 barium chloride solution: HARMFUL
• 0.4 mol/dm3 dilute nitric acid: IRRITANT
• 0.05 mol/dm3 silver nitrate: LOW RISK
• limewater: IRRITANT
Equipment - anion test
Equipment • two test tubes • test tube rack • stand, boss, and clamp • bung and delivery tube • dimple dishes • droppers • limewater • 0.4 mol/dm3 hydrochloric acid • 0.1 mol/dm3 barium chloride solution • 0.4 mol/dm3 nitric acid • 0.05 mol/dm3 silver nitrate solution • known labelled solutions: sodium carbonate, sodium sulfate, sodium chloride, sodium bromide, and sodium iodide
Setting the scene - anion tests
Each anion (negative ion) can be detected using a specific test. In the sulfate test, __ chloride reacts with sulfate ions to produce a __ precipitate of barium sulfate. In the halide test, __ nitrate reacts with chloride, __, and iodide ions to give a precipitate of the silver halide. The carbonate test relies on the fact that acids react with carbonates to give off carbon __.
Setting the scene
Each anion (negative ion) can be detected using a specific test. In the sulfate test, barium chloride reacts with sulfate ions to produce a white precipitate of barium sulfate. In the halide test, silver nitrate reacts with chloride, bromide, and iodide ions to give a precipitate of the silver halide. The carbonate test relies on the fact that acids react with carbonates to give off carbon dioxide.
