HSC Scientific Experiment: Testing for Anions
Published by To carry out a series of chemical reactions in order to devise chemical tests for identifying the following anions in solution where these are the only ions that could be present.
Activity 3 – Tests for Anions
Aim
To carry out a series of chemical reactions in order to devise chemical tests for identifying the following anions in solution where these are the only ions that could be present.
Results
|
|
Test Solution |
||||
|
Anion |
H+ |
Ag+ |
Pb2+ |
Ba2+ |
Ba2+ & OH- |
|
CO32- |
Fizzed, bubbled |
No |
White Precipitate |
White Precipitate |
White Precipitate |
|
Cl- |
No |
White Precipitate |
No |
No |
No |
|
SO42- |
No |
No |
White Precipitate |
White Precipitate |
White Precipitate |
|
PO43- |
No |
Yellow Precipitate |
White Precipitate |
White Precipitate |
White Precipitate |
Questions
1.
|
Anion |
Test and Result |
|
Cl- |
Gives a precipitate with acidified Ag+ but not with Ba2+ |
|
SO42- |
Gives a precipitate with acidified Ba2+ |
|
PO43- |
Gives a precipitate in alkaline solutions but not with acid solutions. |
|
CO32- |
Produce bubbles of gas with addition of dilute HNO3 |
2. Is lead ion useful in identifying anions? Explain why or why not?
Lead ions are not very useful in identifying anions. This can be seen in the fact that it cannot be used to clearly distinguish between any of the four anions. It produces a white precipitate with CO32-, nothing with Cl-, a white precipitate with SO42- and a white precipitate with PO43-. This exactly the same as Ba2+.
3. When identifying anions in a solution where two anions may be present, it is necessary to destroy any CO32-, before testing for other anions can be carried out. How might this be done? (Consider the tests in the experiment.). Why is this necessary?
It is important to destroy any CO32- as it will react with any acid (fizz). Since anions must be acidified before being tested with various test solutions, the CO32- must be destroyed in order for the tests to be carried out without any of the H+ ions from the acid from reaction with the CO32-. This can be done by…
Conclusion
The series of chemical reactions conducted were successful in identifying anions in a solution. As a result, the following process was derived from the experiment:
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On June 29, 2011 at 6:30 pm
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