Six Bottle Problem Activity
Introduction
Materials
Name/Number:__________________________________
Samples of six solutions are found on the counter without chemical names. It is your job to identify the
cation and anion in each of the bottles so you can give the formula of each of the six unknowns. There
are five different cations: ammonium, copper(II), hydrogen, iron(III), and silver(I) There are four
possible anions present in the six bottles. These anions include chloride, hydroxide, nitrate, and sulfate.
*pH paper
Well-plate
*BaCl2(aq), 0.200 M
*Six unknown solutions
*AgNO3(aq), 0.200 M
Pre-Lab Questions
Answer the following questions using complete sentences BEFORE completing the lab.
1. Define cation. Does an atom gain or lose electrons to form a cation?
2. What is a polyatomic ion?
3. Write the symbols, with charges, for the 5 possible cations.
4. Write the symbols, with charges, for the 4 possible anions.
___Check with Mrs. MacLeod
Cation Determination Procedure
1. Place 5 drops of each solution in one row of the well plate, keeping track of which solution is in each well. While
you are getting a sample of each solution, waft them. One solution should have a strong odor, smelling of
ammonia [think cleaning products]. Record a ‘Yes’ in the smell test section for this bottle. The other solutions
will be recorded as a ‘No.’ This solution contains the cation ammonium.
2. Examine each of the six solutions and record the color of each in your data table. The colors will allow you to
determine several cations in the bottles:
Blue = copper(II)
Orange = iron(III)
3. Using both a red and blue piece of litmus paper, test the pH of each solution. Record whether the red litmus paper
turned blue or had no change [record blue or NC, for no change], and whether the blue litmus paper turned red or
had no change [record red or NC]. Solutions which caused the blue pH paper to turn red [and do not already have
a cation identified!] will contain the hydrogen ion.
4. You should have identified the cation in 5 of the bottles. There is only one remaining cation for the last bottle.
Anion Determination Procedure
5. Using the information learned from the pH test, you can identify which solutions contain hydroxide ions. These
will have turned the red pH paper blue.
6. Add a drop of the solution containing silver to each of the remaining solutions with unknown anions in the well
plate from the pH test. Silver is known to react with chloride ions to form a solid (called a precipitate, which will
look cloudy). Record in your data table the solutions turned cloudy or remained clear. Any solution that you do
not test with the silver should be recorded as N/A.
7. Now place 5 new drops of only the solutions that still have unknown anions in a new row on the well plate. Add
a drop of the barium solution to these final unknowns. Barium is known to react with sulfate ions to form a
precipitate. Record which solutions turned cloudy or remained clear; any solution that you do not test with the
barium should be recorded as N/A.
8. The remaining solutions will not cause any reaction, no matter what you add to them. These will all contain the
last remaining possible anion, nitrate.
Clean-up
9. Rinse the well plate thoroughly with water, using a test tube brush as needed in any well. Return your station to
its previous state, put goggles away, wash your hands, and check out with the instructor.
Data/Observations
Bottle
Smell
Color
Red
Litmus
Blue
Litmus
Silver
Test
Barium
Test
Cation
Anion
1
2
3
4
5
6
Questions
1. Write the correct formula for the compound in each bottle. Be sure to include the number for each solution.
2. Name the compound in each bottle, including roman numerals when appropriate. Again, label the number for
each solution.