Embedded Files
Syllabus
Syllabus
Carbonates react with dilute acids to form Carbon Dioxide gas which can be identified with Limewater.
Halide ions in solution produce precipitates with Silver Nitrate solution in the presence of dilute Nitric acid.
Silver Chloride is white, Silver Bromide is cream and Silver Iodide is yellow.
Sulphate ions in solution produce a white precipitate with Barium Chloride solution in the presence of dilute Hydrochloric acid.
Required practical 7: use of chemical tests to identify the ions in unknown single ionic compounds covering the ions from sections Flame tests to Sulphates.
What does this mean?
What does this mean?
Halide ion tests
Halide ion tests
Halide ions are the ions formed by Halogens (Group 7)
For the test to work it must be be acidic.
We use Nitric Acid to acidify the solutions because Hydrochloric acid would add Cl- ions that would show up in the precipitate.
Sulphuric acid would add Sulphate ions which we also often test for.
Once the solution has been acidified a few drops of Silver Nitrate solution will form a differently coloured precipitate with each halide ion.
This happens because when Silver ions (Ag+) meet halide ions they form insoluble solids.
Ag+ (aq) + Cl- (aq)--> AgCl(s) Silver Chloride ppt = White
Ag+ (aq) + Br- (aq)--> AgBr(s) Silver Bromide ppt = Cream
Ag+ (aq) + l- (aq)--> Agl(s) Silver Iodide ppt = Yellow
Sulphate ion test
Sulphate ion test
This test also requires acidifying to work correctly.
Clearly there would be no point acidifying with Sulphuric acid as this contains Sulphate ions.
So, Hydrochloric acid is used.
A few drops of Barium Chloride will form a precipitate since Barium Sulphate is insoluble.
Ba2+ (aq) + SO42- (aq)--> BaSO4(s) Precipitate = White
Carbonate ion test
Carbonates react with dilute acids to produce Carbon Dioxide gas
Carbonate + Acid --> Salt + Water + Carbon Dioxide
So adding a little Hydrochloric acid and allowing the gas produced to bubble through lime-water should produce a milky white precipitate.
Videos
Videos
Chloride ion test
Chloride ion test
Bromide ion test
Bromide ion test
(and others)
Iodide ion test
Iodide ion test
Sulphate ion test
Sulphate ion test
Carbonate ion test
Carbonate ion test
All the above
All the above
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PAST PAPER QUESTIONS
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