Tests for gases 1
Test for hydrogen.
Test: Ignite the gas
Observation: burns with squeaky pop
Test for Oxygen
Test: place a glowing wooden splint in the gas
Observation: Relight splint.
Test for carbon dioxide
Test: bubble gas through lime water
Observation: lime water goes cloudy/milky
Test for gases 2
Test for Ammonia
Test: place damp red litmus paper into gas
Observation: litmus paper goes blue
Test for Nitrogen dioxide
Test: observe colour
Observation: gas is brown
Test for chlorine
Test: place damp litmus paper in the gas
Observation: bleaches rapidly the litmus paper
Test for gas 3
Test for Hydrogen chloride
Test 1: place damp blue litmus paper into gas
Observation: turns blue litmus paper red
Test 2: place the stopper from a bottle of concentrated ammonia in the gas
Observation: white smoke(ammonium chloride) is formed
Test for Sulphur dioxide
Test: place filter paper soaked in potassium dichromate solution in the gas.
Observation: colour changes from orange to green
Clean platinum or nichrome wireis dipped into concentrated hydrochloric acid, then into the solid to be tested and finally into the hottest part of the Bunsen flame.
The concentrated hydrochloric acid convert some of the unknown solid into chlorides.
Chlorides are more volatile than other salts, so some of the unknown goes into gas phase when heated in the hot flame.
Colours of the flame test are produced through the excitation of electrons to higher energy levels, they become unstable and falls to the ground state. Through the process of falling it emits light of colour specific to the metal present in the compound.
- The flame test is the only test for group 1
- Flame test cannot be used on mixtures as the colour produced by one of the ions will mask the colour produced by the other metal ions.
Li+ (crimson) , Na+ (Yellow), K+ (Lilac), Ca 2+ (Yellow-red), Sr 2+ (Red), Ba 2+ (pale green)