Qualitative Analysis Lab Activity
Introduction
Chemists have devised several techniques to identify ions in solution. This is important in the fields of
environmental chemistry and medicine. In many cases, a range of techniques must be used to clearly identify the ions
in a solution. This process of ion-identification is called qualitative analysis.
In this lab you will make and carry out a qualitative analysis plan to identify metal cations present in two
unknown solutions. You will use the three qualitative analysis techniques we learned in class (selective precipitation,
flame colour, and colour of solution).
Use precipitate tests when possible as they are the most reliable. If there is no precipitate test, use a flame
test and double check your results by using the colour of solution.
Each student will have a different combination of metal cations in their sample. All mystery samples contain one or
both ions listed on the side of the sample:
Mystery Solution A: Ba(NO3)2 (aq) and/or AgNO3 (aq)
Mystery Solution B: KNO3 (aq) and/or Ba(NO3)2 (aq)
Mystery Solution C: CuCl2 (aq) and/or Ba(NO3)2 (aq)
Mystery Solution D: Ni(NO3)2 (aq) and/or NaCl (aq)
Mystery Solution E: Ni(NO3)2 (aq) and/or Cu(NO3)2 (aq)
Materials
apron and goggles
2 small test tubes
centrifuge
plastic pipettes
Nichrome wire
test tube rack or beaker to hold samples upright
Bunsen burner
2 mystery samples
Procedure
1. Make a chalk outline on the lab bench around your work area and write your names in chalk at your station.
2. Obtain two mystery solutions from your teacher.
3. Record the sample number and possible ions immediately. If you do not record the sample number
you will have to repeat the experiment.
4. Use your solubility table and your knowledge of flame tests and colour of solution to make a chart for each
sample in the space provided on this lab sheet.
Method for producing a precipitate
1. Always use a separate clean plastic pipette for each solution you use to avoid contaminating your
samples and your reacting solutions.
2. Do NOT contaminate or throw away your sample- it will be used by another class after this experiment.
3. Write down what the mystery solution looks like and what the reacting solution looks like before the
reaction in your observation section. Transfer about 1mL of your first mystery solution to a small test
tube. Add about 1mL of reacting solution and record your observations after the reaction.
4. If there is a precipitate, let it settle to the bottom to obtain a clear supernatant. Use the centrifuge if
needed.
5. Pour the supernat into a clean small test tube and perform the remaining qualitative analysis test on the
supernat.
Method for identifying the flame colour of metal ions
1. Bring the supernat from your test solution to the darker area of the room.
2. Light a Bunsen burner to produce a hot flame with a blue cone.
3. Clean a nichrome wire by dipping it in acid then burning the acid away until you get a steady orange
flame.
4. Dip the nichrome wire into the mystery solution and place the wire into the flame at the top of the blue
cone. Record your observations.
Method for identifying the solution colour of metal ions
1. Observe the colour of your solution and write it down in your observations.
SCH3U
S14
Title Block
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
___________________________________________________________________ (2 marks, C)
Purpose
_____________________________________________________________________________________________
_____________________________________________________________________________________________
________________________________________________________________________(2 marks, C)
Materials and Methods
Refer to Qualitative Analysis Lab Sheet
Observations
Attach your plan and observation charts
Discussion
For each of your samples:
State the possible ions in solution and identify which ones were present.
(2x2 marks,I)
Use your observations from your qualitative analysis tests to explain how you knew which ions are present
or not. (2x 6 marks,I)
Explain why you chose the tests you did. Explain the limitations of each analysis and comment on the
reliability of each test. (2x3 marks)
SCH3U
S14