4.6 - Chemical tests
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what test is used to test for hydrogen
squeaky pop test
what is the method of the squeaky pop test
• collect a sample of gas in a tube • attempt to ignite the gas using a lit splint
what is the positive result for hydrogen in the squeaky pop test
squeaky pop sound
what chemical reaction is taking place during the squeaky pop test
the combustion of H2 to form H2O 2H2(g) + O2(g) –> 2H2O(g) the pop sound is caused by hot gas rushing out of the test tube
what test is used to test for oxygen
glowing splint test
what is the method of the glowing splint test
• collect a sample of gas in a test tube • place a glowing splint into the tube
what is the positive result for oxygen in the glowing splint test
the splint relights
what is the chemical reaction taking place during the glowing splint test
the combustion of the wood in the splint it relights because the pure O2 is more concentrated than the O2 in normal air. this means the wood in the splint combusts faster
what test is used to test for the presence of H2O
copper sulfate test
what is the method of the copper sulfate test
• add anhydrous copper sulfate (CuSO4)
what is the positive result for the presence of H2O
the anhydrous copper sulfate changes from white to blue
what is the test used to test the purity of H2O
measure its boiling point and compare it to 100 degrees C
what is the method of the boiling water test
• measure its boiling point
what is the positive result for the purity of H2O
the closer it is to 100 degrees C the more pure it is
what is the test used to test for carbon dioxide
limewater test
what is the method of the limewater test
• bubble a sample of gas through water
what is the positive result for carbon dioxide
a white precipitate forms - limewater turns cloudy
what is the chemical reaction taking place during the limewater test
limewater is saturated calcium hydroxide solution, Ca(OH)2 it forms a white precipitate of calcium carbonate (CaCO3) when it reacts with CO2 Ca(OH)2(aq) + CO2(g) –> CaCO3(s) + H2O(l)
what is the test used to test for chlorine
damp blue litmus test
what is the method of the damp blue litmus test
• place damp blue litmus paper in a sample of gas
what is the positive result for chlorine
the blue litmus turns white - it bleaches
what is the chemical reaction taking place during the damp blue litmus test
Cl2 is a good bleaching agent, so it easily removes colour from other substances in this test it dissolves into the dampness (H2O) and removes the colour from the litmus
what is the test used to test ammonia
damp red litmus test
what is the method of the damp red litmus test
• place damp red litmus paper in a sample of gas