Periodic Table Practicals

Seite 1

Identifying alkali metals

Background:

Alkali metals and their respective salts burn in oxygen with different colours.

Method:

Three methods by which this experiment can be performed:

1. Sprinkle method

Sprinkle a small amount of metal salt from around 30cm above a Bunsen flame.

2. Spray method

Prepare spray bottles with various solutions of aqueous metal salts.

Spray these directly into the side of a Bunsen flame .

3. Flame probe method

Dip the end of the flame test probe into hydrochloric acid and then into some of the metal salt powder.

Place the probe into the hottest part of the Bunsen flame.

Results:

The salts burn with the following colours:

Sodium: Orange yellow

Lithium: Crimson red

Potassium: Lilac

Seite 2

Identifying halides

Background:

Chlorine: A greenish-yellow gas at room temperature

Bromine: A reddish brown liquid at room temperature

Iodine: Usually found in its salts (iodides)

Methods:

Test for chloride

Place a small amount of sodium chloride, dilute nitric acid and a few drops of silver nitrate solution in a test tube.

White precipitate will form.

Precipitate turns darker in sunlight and dissolves when a dilute solution of ammonia is added.

Test for bromide:

Place a small amount of sodium bromide, dilute nitric acid and a few drops of sliver nitrate in a test tube.

Pale yellow precipitate will form.

Precipitate does not dissolve in dilute ammonia solution, but does dissolve in concentrated ammonia solution.

Test for iodide:

Place a small amount of sodium iodide, dilute nitric acid and a few drops of sliver nitrate in a test tube.

Yellow precipitate will form.

Precipitate is insoluble in ammonia solution.

Chemical equations:

Ag+(aq)+X−(aq)−>AgXl(s

where X is the halide anion