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Flame Test: Lithium (Li)
Red
Flame Test: Sodium (Na)
Yellow Orange
Flame Test: Potassium (K)
Lilac/Pink
Flame Test: Rubidium (Rb)
Red/Violet
Flame Test: Caesium (Cs)
Blue/Violet
Flame Test: Calcium (Ca)
Orange Red
Flame Test: Strontium (Sr)
Brick Red
Flame Test: Barium (Ba)
Pale Green
Flame Test: Copper (Cu)
Blue/Green
Flame Test: Lead
White/Grey
Test for Halide Ions
Silver Nitrate Test
Test done in solution. If starting from solid, sample must first be dissolved in pure water.
Add dilute nitric acid to the samples. This is to remove/react away any interfering ions (carbonate or hydroxide ions) that may give a false positive result/precipitation.
Add silver nitrate solution to the samples and observe the precipitate.
Silver Nitrate Test: Fluoride Ions
no precipitate
Silver Nitrate Test: Chloride Ions
white precipitate
Silver Nitrate Test: Bromide Ions
cream precipitate
Silver Nitrate Test: Iodide Ions
yellow precipitate
Test for Sulphate Ions
Test must be done in solution. If starting from solid, it must first be dissolved in pure water.
Acidify the sample with dilute hydrochloric acid.
Add barium chloride (BaCl₂).
If a sulphate is present, a white precipitate will form (insoluble barium sulphate).
Test for Carbonate Ions
Add a dilute acid to the compound (usually dilute hydrochloric acid).
If carbonate ions are present, they will react with the acid and produce carbon dioxide, which will be observed as bubbles/effervescence.
To test the gas being produced, collect a sample and test with limewater. Carbon dioxide turns limewater cloudy.
Testing Alkenes
Shake an alkene with bromine water, or bubble a gaseous alkene through bromine water.
Alkenes decolourise bromine water, so the solution will become colourless (from brown/orange).
Testing Aldehydes
To test for aldehydes, you can use Fehling’s solution, Tollens’ Reagent or Benedict’s solution.
Fehling’s Solution
blue solution → brick red precipitate (copper (I) oxide)
Tollens’ Reagent
no visible change → silver mirror (coating of silver on surface of test tube, or black precipitate)
Benedict’s Reagent
blue solution
→ green → yellow (low conc. aldehyde)
→ orange → red ppt. (high conc. aldehyde)
Fehling’s Solution
blue solution → brick red precipitate (copper (I) oxide)
Tollens’ Reagent
no visible change → silver mirror (coating of silver on surface of test tube, or black precipitate)
Benedict’s Solution
blue solution
→ green → yellow (low conc. aldehyde)
→ orange → red ppt. (high conc. aldehyde)