Chemical Analysis
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What is test for chlorine?
Chlorine bleaches damp litmus paper = turns it white
If you use blue litmus paper (when testing for chlorine), why might it turn red for a moment?
Because solution of chlorine is acidic
What smell does chlorine have?
Has characteristic sharp, choking smell
What is test for hydrogen?
Burning splint at open end of test tube containing hydrogen = get “squeaky pop”
Where does the noise come from when testing for hydrogen?
Comes from hydrogen burning quickly in oxygen in air to form water
What is the test for oxygen?
Glowing splint inside test tube containing oxygen = oxygen will relight growling splint
What is the test for carbon dioxide?
Bubbling carbon dioxide though limewater = solution turns cloudy
What is test for ammonia?
• Makes damp red litmus paper turn blue • Forms a white smoke of ammonium chloride when hydrogen chloride gas (from concentrated hydrochloric acid) is held near it
What is the test for sulfate ions?
• Use dropping pipette to add a couple drops of dilute hydrochloric acid (HCl) • Followed by couple drops of barium chloride solution (BaCl2) to test tube containing mystery solution • If sulfate ions are present = white precipitate of barium sulfate will form
What is the test carbonate ions?
• Using a dropping pipette to add few drops of dilute acid to test tube containing mystery substance • Then connect test tube to test tube containing limewater • If carbonate ions are present = reaction with acid will release CO2 = turns limewater cloudy when it bubbles through • Turns cloudy white bc carbon dioxide produces = a white precipitate
What is the test for halide ions (Cl-, Br-, I-)?
• Add couple drops of dilute nitric acid (HNO3) • Followed by couple drops of silver nitrate solution (AgNO3) to mystery solution
In the test for halide ions, what does chloride give?
White precipitate of silver chloride
In the test for halide ions, what does bromide give?
Cream precipitate of silver bromide
In the test for halide ions, what does iodide give?
Yellow predicate of silver iodide
How can you test for metal ions?
By heating your substance and seeing whether the flame turns a distinctive colour → use these colours to detect & identify different ions
Describe the method for testing for metal ions
• Clean nichrome or platinum wire loop by rubbing with fine emery paper • Hold it in blue flame Bunsen burner • Flame might change colour but once it’s blue again = loop is clean • Dip loop into sample you want to test & put back in flame • Record colour of flame
Why does the method for testing for metal ions only work for samples that contain a single metal ion?
If sample tested contains a mixture of metal ions = flame colours of some ions may be hidden by colours of others
What colour flame do lithium ions produce?
Crimson
What colour flame do sodium ions produce?
Yellow
What colour flame do potassium ions produce?
Lilac
What colour flame do calcium ions produce?
Orange-Red
Many metal hydroxides are…
Insoluble and precipitate out of solution when formed
What is the test for (some) metals?
• Add few drops of sodium hydroxide solution to a solution of your mystery compound • If you get a coloured precipitate (insoluble hydroxide) = can tell which metal was in the compound
What is the colour of the precipitate that calcium ions forms?
White