Ahmet Tuğrul AKKUŞ
18.10.2011
11-B 103
Design
Research Question
By which methods can we separate anions and cations of different compounds in chemistry?
Procedure
Apparatus
1)9 test tubes
2) Test tube rack
3) Gloves
5) Lab coat
6) 0.2 M solutions of anions (NaCl, KI, Na2CO3, Na2SO4, NaNO3), cations (AgNO3, Cu
(NO3)2, Pb (NO3)2, Fe (NO3)2)
8) Stirrer
10) Silver nitrate solution (0.5 M)
12) Sodium hydroxide solution (0.5M)
14) Barium chloride solution (0.5 M)
15) Magnesium nitrate solution (0.5M)
15) Aluminum foil
17) Beakers
18) Bunsen burner
19) Tripod
20) Wire gauze
21) Fume cupboard
In this experiment anions and cations are going to be analyzed and separated. 0.2 M anions
Cl- , I-, (CO3)-2, (SO4)-2, (NO3)-1 and 0.2 M of Ag+, Cu+2, Pb+2, Fe+2 cations are set to be
identified.
At the beginning of the experiment, anions and cations will be set as separated from each
other. Lab coat and gloves are used for safety.
There were 5 anion solutions and 5 labeled test tubes were used for the experiment. Samples
were taken from the Erlenmeyer flasks by pipette.
First nitric acid was used to acidify anion solutions, then silver nitrate solution is added to the
test tubes, so the one containing chloride ions will form a white precipitate composed of silver
chloride. Also the one containing iodide ions will form silver iodide which is a yellow solid
precipitate.
Magnesium nitrate is added to remaining test tubes and the one containing carbonate ions will
form magnesium carbonate which is a white solid precipitate.
Then remaining anions are sulphate and nitrate ions. To the remaining test tubes barium
chloride solution is going to be added so the test tube containing sulphate ions will form a
barium sulphate which is a white precipitate.
Remaining unidentified sample is (NO3)-. Test tube is poured into a beaker then a little
sodium hydroxide and aluminum foil is added to the solution and it is heated on Bunsen
burner carefully. This process must be carried in a fume cupboard since ammonia is given off.
Then while heating the sample, a litmus paper is held into the mouth of the test tube and a
color change from red to pink is observed and it is a proof of the existence of nitrate ions in
the solution.
Now it is time for cation group. The test tubes were labeled as in the order they were taken
from the Erlenmeyer flasks by pipette. A few drops of dilute sodium hydroxide is added four
test tubes. Cu+2 form a pale blue precipitate as copper (II) hydroxide is insoluble in water.
Also Fe+3 form a red brown precipitate with dilute sodium hydroxide. Pb+2 formed a white
precipitate with a few drops of dilute sodium hydroxide and Ag+2 form a light brown
precipitate with sodium hydroxide solution.
It is better to gather the data in two tables for cations and anions
TEST TUBES
1)
2)
3)
4)
5)
ANIONS
Chloride
Iodide
Carbonate
Nitrate
Sulphate
All anion samples were identified successfully by the method described above.
TEST TUBES CATIONS
1)
Ag+2
2)
3)
4)
Cu+2
Pb+2
Fe+3
All cation samples were clearly identified and all expected precipitations was observed so the
cations in the test tubes follows as the table above.
As a conclusion all of the samples were identified successfully because they all gave the
expected reactions with the known solutions. Solutions were not prepared with sensitivity
because as the experiment did not include any graphical data or graphical interpretation but
just to show the presence of the anions and cations, the concentration of the solutions were not
considered important as it will not change the result of the experiment. It was same for the
amount of samples taken by each Erlenmeyer flask; we did not measure the volume of sample
taken from the Erlenmeyer flasks for the same reason. Calculating the concentration of all the
solutions that had been prepared would be a good improvement for the scientific being of the
experiment and also the volume of sample taken from each Erlenmeyer could be measured for
the welfare of the experiment. Another improvement could be repeating the experiment by
using other kind of solutions that would have different identifications for anions and cations
so that we could support our answers by two different experiments.
At the beginning of the experiment, the research question was “By which methods can we
separate anions and cations of different compounds in chemistry?” and the answer to the
question is to use displacement reactions taking place between any ion in the solution and the
solution being added and making sure that the new compound does not dissolve in water and
forms a precipitate so that it is easier to identify the substance.