Chemical Tests

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Testing For Ammonium

Testing for carbonate anions
Metal carbonates, which contain CO32- ions, are identified by the addition of a few drops of dilute hydrochloric acid. A colourless gas is given off as the carbonate ions react with the hydrogen ions.

Testing for halide anions
(Chlorine, Bromine and Iodine). They are detected by adding nitric acid and then silver nitrate solution. If halides are present, a precipitate will form (silver halides)

Add NaOH and ammonia together in a test tube

Put that test tube into a beaker that’s above the bunsen burner

Add damp red litmus paper in

Turns blue if ammonium is present.

Test for anhydrous copper(II) sulfate
Get a plastic tray and scoop anhydrous copper sulphate into it then put 1 drop at a time of water, you will observe the white anhydrous copper sulphate turn into hydrated copper sulphate crystals. The crystals will release heat because it is a reverse process. If heat is used to evaporate water then water has to be released.

Sodium Iodide: A flame test gives a yellow flame after adding Nitric acid followed by a silver nitrate, a yellow precipitate is made

Hydrochloric acid is added when you are testing for a sulphate because The acid reacts with any carbonate ions in a solution and gets rid of carbonates ion in the solution.

Can’t use HCl to try and identify chloride as chloride is in HCl

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Dangers of the Gases:

CO2 - Poisonous

O2 - in high concentrations will cause things to ignite

H2 - highly explosive

NH3 - smelly and poisonous

Cl2 - poisonous

Test for the gases

Hydrogen (H2) - Squeaky pop test: Put HCl and Mg in a test tube and hold the top then light a splint and put in the test tube and it should pop.

Carbon Dioxide (CO2) - Put lime water into the gas and it should turn cloudy

Oxygen (O2) - Light a splint, blow it out and while still glowy put it in oxygen and it should re ignite if oxygen is present.

Ammonia (NH3) - Insert damp red litmus paper and if it turns blue, ammonia is present (because it’s and alkali)

Chlorine (Cl2) - Insert damp UI paper into the gas. If the paper turns red then bleaches, chlorine is present

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Note the colour

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Dip the nichrome wire loop into dilute HCl

Place in blue (non-luminous) bunsen flame to clean it.

Dip into the HCl again and then the compound you’re going to test.

Place the wire into the blue Bunsen flame

Note the colour