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CHEMICAL TESTS (GAS TESTS + OBSERVATIONS (CARBON DIOXIDE (Bubble a gas…
CHEMICAL TESTS
GAS TESTS + OBSERVATIONS
CARBON DIOXIDE
Bubble a gas through limewater. If it is carbon dioxide, the solution should turn cloudy white.
AMMONIA
Makes damp litmus paper (red) turn blue. It also forms white smoke of ammonium chloride when in contact of hydrogen gas.
OXYGEN
A lighted splint burns to a faint ember, and is introduced to a gas sample. If exposed to oxygen, the match should light again.
CHLORINE
Makes damp litmus paper (blue) turn red, then white. It also makes damp starch iodide paper turn blue-black.
HYDROGEN
A test tube has a splint lit near the opening of the tube. The stopper is removed to expose the splint to the gas. If the gas is hydrogen, it will make a 'pop' sound.
APPLICATION
ANION TEST
The purpose of anion tests are to detect ions present in a solution based on the precipitate that they form. In everyday life, anion tests might be useful in the process of chromatography
GAS TEST
Gas tests are used, as some gases can be hard to distinguish by their sight or smell, as they are colourless and odourless. Tests involving burning splints can be used to indicate the flammability of certain gases. Certain gases can also turn solutions different colours, and have acidity/alkali properties, thus reacting to litmus paper.
FLAME TEST
This test allows you to identify unknown metals, as each metal produces a unique colour when exposed to a flame. In real life, the flame test can be applied in atomic absorption spectroscopy and atomic emission spectroscopy to quantify the metals that are used in a sample.
SODIUM HYDROXIDE TEST
This test is used to test and identify metal ions based on the precipitate that they form. Like the anion tests, they might be also useful in the process of chromatography.
CATION TESTS
SODIUM HYDROXIDE TESTS
INSTRUCTIONS
- If a coloured precipitate is formed, identify what the cation is.
- If a white precipitate forms, continue to add more sodium hydroxide to it and see if the precipitate dissolves.
- Add several drops of sodium hydroxide solution to the solution being tested.
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FLAME TESTS
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INSTRUCTIONS
- Once done with the substance, clean the rod with HCL to test other substances. To check that it's clean, hold the rod up to the flame. If there is a burst of colour, it isn't clean, but if there's no distinct colour, it is ready for more testing.
- Repeat steps 2-3 until you have tested all of the substances
- After the rod is cleaned, dip it into the hottest part of the flame, the edge covered with the substance you are testing.
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- Clean the nichrome wire with hydrochloric acid, then hold it up to a lighted Bunsen burner flame. It is clean when the rod stops changing colour.
ANION TESTS
If you have an unknown substance, but want to find to find out what sort of anion it is, you can use these methods to find out what it is.
Add nitric acid
GAS PRODUCED?
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No
Add silver nitrate
PRECIPITATE FORMED?
Yes
COLOUR OF PPT OBSERVED
- 3 more items...
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DETECTING WATER
INSTRUCTIONS
- Continue heating until colourless droplets condense on the inner mouth of the test tube.
- Put a piece of anhydrous cobalt (II) chloride paper to contact the droplets using a pair of forceps and observe the results. We find the paper changes from blue to pink.
- Hold the test tube with the mouth sloping downwards and heat the end of the tube slowly with a Bunsen burner. It is advised you hod the tube with pliers to prevent the droplets from flowing back to the hot end of the test tube and cracking it.
- Add a spatula of copper (II) sulfate 5 water into a dried test tube