In this part of the lab you will be given practice samples to try your qualitative skills on.
You should repeat all tests on the practice samples that are available. The more you do the more confident you will be when you work with your final unknowns during the lab exam.
2+
2+
3+
3+
+
+
+
Step 1
Examine the original solution and note any colour or other obvious characteristics of the solution. In many cases, these can serve as an indication of some of the ions present or absent.
Step 2
Place five drops of the solution in a centrifuge tube. Add one drop of HCl(aq). Mix thoroughly and, if a precipitate appears, centrifuge. Add another drop of HCl(aq) to the solution to determine if precipitation is complete. Repeat until precipitation is complete.
The presence of a precipitate indicates the Ag + ion. Centrifuge the mixture and remove the solution for further analysis. You may discard the precipitate.
Step 3
To the solution from step 2, add NH
4
OH(aq). The appearance of a deep blue colour in the solution at this stage indicates the presence of copper due to a copper ammonia complex ion, Cu(NH
3
)
4
2+ (aq).
If a flocculent precipitate appears, stir vigorously, centrifuge and decant, keep the decantate for step 5 and the precipitate for step 4.
Step 4
To the precipitate from step 3 add several drops of NaOH(aq). If some, or all, of the precipitate dissolves, this indicates the presence of Al 3+ (aq). To confirm, centrifuge and decant. To the decatate, add HCl(aq) drop by drop, until blue litmus paper turns red. If
Al 3+ was present in the sample, Al(OH)
3
(s) will form.
If a reddish brown precipitate remains after the addition of the NaOH(aq), then Fe 3+ (aq) was present. To confirm, dissolve the precipitate in HCl(aq). Now add potassium ferrocyanide drop by drop. A dark blue colour indicates the presence of Fe 3+ (aq)

Step 5
To the decantate from step 3 carefully add several drops of NaOH(aq). If a precipitate appears, this indicates the presence of Ca 2+ (aq).
Step 6.
Perform flame tests on the original sample for Na + (aq) and K + (aq)
4
2-
3
2-
-
-
Step 1
Place five drops of the solution in a centrifuge tube. Add one drop of barium nitrate.
Mix thoroughly and, if a precipitate appears, centrifuge. Add another drop of barium nitrate to the solution to determine if precipitation is complete. Repeat until precipitation is complete. Centrifuge the mixture and remove the solution with a pipet. The presence of a precipitate indicates the presence of the CO
3
2- and/or SO
4
2 ion. Save the solution and precipitate for further analysis.
Step 2
To the precipitate from step 1 add 5 drops of HNO
3
(aq). Mix thoroughly and centrifuge.
If the precipitate disappears entirely then only CO
3
2 was present. If you are unsure add
HNO
3
(aq) drop by drop and observe carefully. If a precipitate remains after the
HNO
3
(aq) is added then SO
4
2 was present. No further analysis is necessary.
Step 3
To the solution from step 1, add drop by drop AgNO
3
(aq). If a precipitate forms, then
Cl (aq) and/or I (aq) is present. Add the AgNO
3
(aq) until precipitation ceases. Mix thoroughly and centrifuge. Remove and discard the solution. Save the precipitate for further analysis.
Step 4
To the precipitate from step 3 add 10 drops of NH
4
NO
3
(aq). Mix thoroughly and centrifuge. If a yellow precipitate remains, then I (aq) was present. The precipitate may change colour due to the bleaching action of NH
4
NO
3
(aq). Remove the solution for further analysis. (You may discard the precipitate).
Step 5
To the solution from step 4, add HNO
3
(aq). If a precipitate forms then Cl was present.

Lab Exam
In this part of the lab you will obtain two unknown samples. Each unknown will contain a given number of ions selected from the following:
The first unknown sample will contain any four of the following cations:
Ca 2+ Cu 2+ Al 3+ Fe 3+ Ag + Na + K +
The second unknown sample will contain any two of the following anions:
SO
4
2- CO
3
2 Cl I -
You will repeat all of the tests and procedures you performed in part B on your two unknowns in order to determine which cations and which anions are present. After you have completed the tests to your satisfaction you will turn in two cards which contains your name, lab section, unknown numbers and the list of ions you determined were present in each unknown.
This card will be returned to you graded out of 10. Any errors will be indicated on the cards.
Lab Write-up
The lab write-up will also count for 10 marks. The write-up will relate only to how you determined the ions in your unknowns. The write-up will be a combination of your procedure and observations. At each procedure step you should indicate which ions you found or eliminated from the unknown.
Conclusion
If you did not get all the ions right in both unknowns, you must explain your mistakes.
Be sure to discuss the method used and its limitations.
Your cards must also be turned in with your lab write-up.