Flame test for cations
The flame color of group 1, 2, and one Transition group metals.
A number of common metal ions (Li+, Na+, K+, Ca2+, Ba2+, Sr+, and Cu2+) give a distinct color to aflame. Therefore, a flame test is often used as a confirmatory test in identifying an unknown metal.
Solutions listed below in the table
The Bunsen burner’s flame should be blue and the metallic (more frequently nichrome alloy) loop placed on the tip of the blue inner cone of the flame.
First, wash the loop dipping it into hydrochloric acid, rinsing with distilled water and checking the flame is no longer colored, so you are sure the test is not invalidated by any previous experiments.
Put some crystals of sample or dip it into the solution to be tested.
Put the loop once again on the tip of the inner blue cone of the flame and observe.
Name of compound | Cation | Observation |
Barium chloride | Ba2+ | Orange |
Potassium chloride | K+ | Reddish orange |
Copper chloride | Cu2+ | Blue green |
Calcium chloride | Ca2+ | Red |
Lithium chloride | Li+ | Vibrant red |
Sodium chloride | Na+ | Orange |
Strontium chloride | St2+ | Dark orange, hot pick |
Test tube reactions to identify anions
Result of test tube reactions
Test | Observation | Inference |
Carbonate | Limewater turns milky | Carbonate(CO32-) is present |
Chloride | Thick white precipitate | Sample contains chloride(cl) |
Bromide | Cream precipitate | Sample contains Bromide(BR-) |
Iodide | Pale yellow precipitate | Sample contains Iodide(I-) |
Sulphate | White precipitate does not dissolve in dilute hydrochloric acid | Sample contains SO42- ion and it’s a sulphate |
Sulphite | White precipitate does dissolve in dilute hydrochloric acid | Sample |
Halides | No precipitate seen | Sample does not contain halides ion |
Reaction with sodium carbonate