Chemical Tests
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What are the 3 gas tests?
hydrogen: pop test oxygen: ignite/flame test carbon dioxide: limewater test
How do you test for hydrogen?
you take a lit split (flame) and touch it to the top/opening of a test tube fill with gas. if the the gas in the test tube contained hydrogen a pop sound will occur. if not, then the gas doesn’t contain any hydrogen.
How do you test for oxygen?
oxygen supports combustion, so if you take a lit splint (flame) and touch it to the top of a test tube filled with the gas, if it relights with a flame then oxygen is present in the gas.
How do you test for carbon dioxide?
carbon dioxide reacts with limewater forming white precipitate. so pass the gas through a container of limewater and if it turns cloudy white then carbon dioxide is present.
What is limewater?
a solution of calcium hydroxide (CaOH)
What are the flame tests for?
to test for cations and anions
Describe the process of a flame test
• dip wire loop in HCl and heat it in the flame until no colour appears to clean it • dip wire loop in the substance and then into the flame • observe the colour of the flame
What are the colours of the flame test and what do they mean?
red = Li+ yellow = Na+ lilac = K+ orange = Ca2+ blue/green = Cu2+