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Chemical Tests (Gas test (Chlorine (Oxygen (To test for Oxygen, take a…
Chemical Tests
Gas test
Chlorine
Oxygen
To test for Oxygen, take a glowing splint, and place it in the gas suspected of being oxygen. If the splint relights, it proves the presence of oxygen
When testing for chlorine, take a damp piece of blue litmus paper, and place it in the test tube containing the suspected chlorine gas. If chlorine is present, you will observe the blue litmus paper turn red, and then possibly bleach.
Ammonia
When testing for Ammonia, take a damp piece of red litmus paper, and place it in the test tube with the suspected ammonia gas. You will observe the paper turn from red to blue if ammonia is present
Carbon Dioxide
There are two tests to show whether gas is Carbon Dioxide. The first is to place a lit splint into the gas suspected of being Carbon Dioxide. The flame should go out. The second test involves lime water. When Carbon Dioxide interacts with Lime Water, the Limewater turns cloudy. If you had an experiment, you could link up the test tube to one full of Limewater.
Hydrogen
When a lit splint is placed in a gas suspected of being hydrogen, the flame will go out and a pop sound will be made.
Cation
Flame Test
To do a flame test, dip the wire loop into conical flask of hydrochloric acid and then into the solid compound you wish to test and then place in Bunsen flame. If you wish to test a solution dip the wire into the solution and then into the flame. The flame will turn a different colour, in response to certain elements being present
Lithium
When a flame test is conducted on Lithium, the flame should turn red
Sodium
When a flame test is conducted on Sodium, the flame should turn yellow
Potassium
When a flame test is conducted on Potassium, the flame should turn lilac
Calcium
When a flame test is conducted on Calcium, the flame should turn an orange red or brick red
Barium
When a flame test is conducted on Barium, the flame should turn an Apple Green
Copper
When a flame test is conducted on Copper, the flame should turn a turquoise/ blue green
Another test for Cations involves the use of Sodium Hydroxide. When added to aqueous solutions, these will form precipitates.
Aqueous solutions
calcium Ca2+ When Sodium Hydroxide is added to Calcium, you will observe that a white precipitate is formed. If ammonium is added, this precipitate will dissolve again
magnesium Mg2+ When sodium hydroxide is added to Magnesium, you will observe that a white precipitate forms. This precipitate is insoluble, as adding ammonia does not dissolve the precipitate
copper Cu2+ When sodium hydroxide is added to copper, you will observe that a light blue/ blue precipitate forms. When ammonia is added, the precipitate dissolves again
iron (II) Fe2+ When sodium hydroxide is added to Iron 2+, you will observe a grey green precipitate being formed. It is insoluble. When ammonium is added, the precipitate does not dissolve
iron (III) Fe3+ When Sodium Hydroxide is added to Iron 3+, you will observe a brown red precipitate form. When ammonium is added, it does not dissolve, meaning the precipitate is insoluble
aluminium Al3+ When Sodium Hydroxide is added to Aluminium, you will observe a white insoluble precipitate form. Adding ammonium will not dissolve this.
Anions
Tests
Sulphates
To test for sulphates, add dilute hydrochloric acid (aq) and then barium chloride (aq) The hydrochloric acid is added to remove any carbonate ions present
If a sulphate is present, then a white precipitate is formed
Halides
Halides are identified by adding dilute nitric acid (aq) then silver nitrate (aq) and then adding NH3 in excess
If chloride is present, then you will observe it produce a white precipitate
If Bromide is present, then you will observe it form a cream precipitate
If Iodine is present, then you will observe it form a yellow precipitate
Carbonates
To test for carbonates, use Hydrochloric Acid, carbon dioxide will form if it is a carbonate. Run the gas produced through a test tube with limewater and if the limewater turns cloudy, there was a carbonate present