chemical tests
cations
gas tests
anions
hydrogen
ammonia
chlorine
squeaky pop
chlorine gas test
litmus paper
oxygen
carbon dioxide
Sodium Hydroxide Test
flame test
The Flame test involves exposing the compound to a flame and identifying the compound by the flame color produced. When the compound is heated, the electrons move to energy levels that are higher. This movement makes the ions energetically unstable and they move back into the previous energy join. As they move back, the ions release light energy.on the type of ions, this light energy is different and produces differing colors of flame.
This test uses sodium hydroxide or aqueous ammonia to test and identify metal ions by the precipitation formed. Sodium Hydroxide or Aqueous Ammonia is added to the solution being tested and the color of precipitation formed allows for identification of the compound.
Sulphate and Sulphide
Carbonate
Ion CO32-, carbonate is found in limestone, or calcium carbonate (CaCO3).
To test for it, you must first: Add a dilute acid to the sample. A gas is given off which when tested should prove to be carbon dioxide.
Sulphate is SO42- and Sulphide is SO32-By adding barium chloride to the solution you are testing, a white precipitate will form. If you add hydrochloric acid, the sulphate (SO42-) will not dissolve and the sulphite (SO32-) will.
halogen tests
The test for halogens, or halide ions, is to add silver nitrate to a solution. Often, nitric acid is added first as well. If there are chloride, bromide or iodide ions in the solution they will react with silver to form a precipitate. The different precipitates are summarized in the table below.
A splint is lit and held near the opening of the tube, then the stopper is removed to expose the splint to the gas. If the gas is flammable, the mixture ignites. This test is most commonly used to identify hydrogen, which ignites with a pop sound.
Ammonium ions can be identified in a solution by adding dilute sodium hydroxide solution and gently heating. If ammonium ions are present, they will be converted to ammonia gas. Ammonia has a characteristic choking smell. It also turns damp red litmus paper or damp universal indicator paper blue.
The simplest test for chlorine is a litmus paper test, chlorine will turn a damp blue litmus paper red, and then it'll bleach it white, there are other tests you can perform. For example, chlorine will turn damp starch-iodide paper which is white to a blue- black color.
limewater test
glowing splint
The glowing splint test is a test for an oxidising gas, such as oxygen. In this test, a splint is lit, allowed to burn for a few seconds, then blown out by mouth or by shaking. Whilst the ember at the tip is still glowing hot, the splint is introduced to the gas sample that has been trapped in a vessel.
Carbon dioxide. Carbon dioxide turns limewater milky. A lighted wooden splint goes out in a test tube of carbon dioxide but this happens with other gases, too. So the limewater test is a better choice.