Halide ions
To test for halide ions, add dilute nitric acid (HNO3) followed by silver nitrate solution (AgNO3). A precipitate will be produces, the colour of this precipitate will determine what ions are present.
Cl - > white precipitate
Br- > cream precipitate
I- > yellow precipitate
NOTE: The silver nitrate solution determines which halide ions are present. The dilute nitric acid is added to 'get rid' of an carbonate or sulphite ions (as these would react with the silver nitrate).
Sulphate ions
To test for sulphate ions (SO42- ), add dilute HCl and then barium chloride solution (BaCl2). If sulphate ions are present, a note precipitate would form (this precipitate is barium sulphate)
NOTE: The HCl is used to 'get rid' of any carbonate ions, and these may impede results if present as they would also produce a precipitate).
Carbonate ions
To test for carbonate ions (CO32- ), add dilute HCl to the sample you are testing. If a gas is produced, collect it and bubble it through limewater. If carbonate ions are present, the limewater will go cloudy as carbon dioxide will be released.
Showing posts with label tests for ions and gases. Show all posts
Showing posts with label tests for ions and gases. Show all posts
Wednesday, 18 May 2016
Thursday, 31 March 2016
2.39 describe tests for the gases
Hydrogen
Squeaky pop test - put a lit splint into a test tube of gas. If it makes a 'squeaky pop' sound, hydrogen is in the tube.
Oxygen
Oxygen will relight glowing splint.
Carbon Dioxide
If bubbled through limewater the limewater will go cloudy if carbon dioxide is present.
Ammonia
Damp red litmus paper will turn blue if ammonia is present.
Chlorine
Turns damp blue litmus paper red, then white (as it bleaches).
Squeaky pop test - put a lit splint into a test tube of gas. If it makes a 'squeaky pop' sound, hydrogen is in the tube.
Oxygen
Oxygen will relight glowing splint.
Carbon Dioxide
If bubbled through limewater the limewater will go cloudy if carbon dioxide is present.
Ammonia
Damp red litmus paper will turn blue if ammonia is present.
Chlorine
Turns damp blue litmus paper red, then white (as it bleaches).
2.37 describe the tests for the cations...
Flame tests
To do a flame test, dip a platinum wire loop in dilute HCL then hold it in a flame, take it out once the flame burns without a colour (this means the platinum is clean). Dip the loop in the sample your testing and put it back in the flame, the colour of the flame will tell you what metal ion is in the substance...
Li+ > burns with a crimson red flame
Na+ > burns with a yellow-orange flame
K+ > burns with a lilac flame
Ca2+ > burns with a brick red flame
Sodium hydroxide solution and identify the ammonia evolved (NH4+)
You can check for ammonia gas using damp red litmus paper (will turn from red to blue is ammonia is present).
To test for ammonium ions in an unknown substance, add a few drops of sodium hydroxide solution to a solution of the unknown substance (in a test tube). Hold a piece of litmus paper near the top of the test tube, if ammonia is being given off, ammonium ions are present in the unknown substance.
Sodium hydroxide
Metal hydroxides are insoluble and precipitate out of solution when formed.
For this test add a few drops of sodium hydroxide solution to a solution the 'mystery compound' (what your testing). This will form an insoluble hydroxide. Some of these hydroxides have characteristic colours, this can be used to tell which metal ions are present in the unknown solution...
Cu2+ > blue
Fe2+ > sluggish green (yes, they are genuinely the words used)
Fe3+ > reddish brown
To do a flame test, dip a platinum wire loop in dilute HCL then hold it in a flame, take it out once the flame burns without a colour (this means the platinum is clean). Dip the loop in the sample your testing and put it back in the flame, the colour of the flame will tell you what metal ion is in the substance...
Li+ > burns with a crimson red flame
Na+ > burns with a yellow-orange flame
K+ > burns with a lilac flame
Ca2+ > burns with a brick red flame
Sodium hydroxide solution and identify the ammonia evolved (NH4+)
You can check for ammonia gas using damp red litmus paper (will turn from red to blue is ammonia is present).
To test for ammonium ions in an unknown substance, add a few drops of sodium hydroxide solution to a solution of the unknown substance (in a test tube). Hold a piece of litmus paper near the top of the test tube, if ammonia is being given off, ammonium ions are present in the unknown substance.
Sodium hydroxide
Metal hydroxides are insoluble and precipitate out of solution when formed.
For this test add a few drops of sodium hydroxide solution to a solution the 'mystery compound' (what your testing). This will form an insoluble hydroxide. Some of these hydroxides have characteristic colours, this can be used to tell which metal ions are present in the unknown solution...
Cu2+ > blue
Fe2+ > sluggish green (yes, they are genuinely the words used)
Fe3+ > reddish brown
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