Laboratory Activity:
Identification of Anions & Cations in Solution (Qualitative Analysis)

Purpose:
1. To identify common anions and cations in solution using simple chemical tests.
2. To use these simple tests to identify ions in an unknown solution.

Procedure:
1. Clean test tubes thoroughly and rinse with distilled water before each test. (Measure 2mL one time,
    and create a standard by using a berol pencil to mark the 2mL level in the test tube. Estimated 2mL
    samples will be used in this experiment.)

Part A: Testing for Anions

1. Test for the chloride ion (Cl^-). Add 2mL of sodium chloride (NaCl) solution to one test tube and 2mL of
    the unknown solution to a second test tube. Add 2mL of 6M nitric acid (HNO₃) to each test tube and then
    gently flick the tubes to mix the contents. Caution: Nitric Acid is extremely corrosive. Add 10 drops of
    silver nitrate (AgNO₃) solution to each tube. Flick the tubes to mix. Record observations.

2. Test for the sulfate ion (SO₄^2-). Add 2mL of sodium sulfate solution to one prepared test tube and 2mL
    of the unknown solution to another tube. Add 2mL of 6M hydrochloric acid (HCl) to each tube. Caution:
    Hydrochloric Acid is extremely corrosive. Flick to mix. Add 10 drops of barium chloride solution to
    each test tube. Flick to mix. Record observations.

3. Test for the hydrogen carbonate ion (HCO₃^-). Add 2mL of sodium bicarbonate(NaHCO₃)
    solution to one prepared test tube and 2mL of the unknown to another tube. Carefully observe the test
    tubes as you add 2mL of 6M HCl to each tube. Caution: Hydrochloric Acid is extremely corrosive.
    Record observations.

4. Test for phosphate ion (PO₄^3-). Add 2mL of sodium phosphate(Na₃PO₄) solution to one test tube and
    2mL of the unknown to another tube. Add 1mL of 6M nitric acid (HNO₃) and 10 drops of ammonium
    molybdate [(NH₄)₂MoO₄] solution to each tube. Caution: Nitric Acid is extremely corrosive. Flick to
    mix. Record observations.

Part B: Testing for Cations

1. Test for iron (III) ion (Fe³⁺). Add 2mL of iron (III) sulfate [Fe₂(SO₄)₃] solution to one test tube and
    2mL of the unknown to another tube. Add 5 drops of 3M sulfuric acid (H₂SO₄) and 5 drops of
    potassium thiocyanate (KSCN) solution to each tube. Caution: Sulfuric Acid is extremely corrosive.
    Flick to mix. Record observations.


Laboratory Activity:
Identification of Anions & Cations in Solution (Qualitative Analysis)

Names:_____________________                                           

            _____________________                                           
 

Date:_____________________                                           

Period:________Group:________                                           

Part B: Testing for Cations

2. Flame test for the sodium ion (Na⁺). Add 2mL of sodium chloride (NaCl) solution to one test tube and
    2mL of the unknown solution to a second test tube. Add 3 drops of 6M hydrochloric acid (HCl) to each
    tube. Caution: Hydrochloric Acid is extremely corrosive. Flick to mix. Add 4mL of 6M hydrochloric
    acid (HCl) to a third tube in the test tube rack. Grasp one end of a 10cm nichrome wire using a pair of
    crucible tongs. Heat the looped end of the wire in a hot burner flame. While it is still hot, dip the end of
    the wire into the HCl acid in the test tube. Remove the wire from the acid and immediately reheat it in
    the flame. Repeat the acid cleaning until the color of flame remains unchanged when the wire is inserted.
    Now dip the clean wire into the sodium chloride (NaCl) solution. Immediately hold it in the hot flame.
    Observe and record observations. It may be necessary for you to repeat the cleaning step and test the
    sample again. Test the unknown solution in the same manner. Observe and record observations. Save the
    prepared cleaning solution, the unknown sample and the nichrome wire for the next flame test.


3. Flame test for the potassium ion (K⁺). Add 2mL of potassium chloride (KCl) solution to one test tube
    and use the 2mL of unknown solution from step 2. Add 3 drops of 6M hydrochloric acid (HCl) to each
    tube. Caution: Hydrochloric Acid is extremely corrosive. Clean the nichrome wire as above and test
    the KCl solution. Clean the wire and test your unknown. If your sample contains sodium, the color of the
    flame will mask the color that is characteristic of potassium. You will be able to see the potassium color,
    if it is there, by looking at the flame through a piece of cobalt blue glass. Record observations.

4. Test for calcium ion (Ca²⁺). Add 2mL of calcium nitrate [Ca(NO₃)₂] solution to one test tube and
    2mL of the unknown solution to a second test tube. Add 10 drops of sodium oxalate (Na₂C₂O₄) solution.
    Record observations. Perform a flame test for calcium. Add 3 drops of 6M hydrochloric acid (HCl) to
    fresh 2mL samples of the calcium nitrate solution and the unknown solution. Perform flame tests as
    above recording the color of the calcium flame and that of your unknown.

5. Test for the ammonium ion (NH⁴⁺). Add 2mL of ammonium nitrate (NH₄NO₃) to one test tube and 2mL
    of unknown to a second tube. To each tube, add 3 drops of 6M sodium hydroxide (NaOH). Caution:
    NaOH can cause severe burns. Hold the tube containing the ammonium nitrate solution in a test tube
    holder and gently warm it along its sides with a back and forth motion through the flame. Do not allow
    the solution to boil. At all times make sure the opening of the tube is pointed away from everyone.
    Moisten a piece of red litmus paper with distilled water and hold it above the mouth of the test tube.
    Wave the vapors and sniff cautiously. Repeat these tests for the unknown and record observations.






Laboratory Activity:
Identification of Anions & Cations in Solution (Qualitative Analysis)

Names:_____________________                                           

            _____________________                                           
 

Date:_____________________                                           

Period:________Group:________                                           

Data: Unknown Number______

Results and Conclusions:

1. List the anions present in your unknown.


2. List the cations present in your unknown.


3. Which is more conclusive, a positive or a negative result? For example, if no precipitate forms when silver
    nitrate is added to a solution, you conclude that chloride ions are not present, if a precipitate is formed
    when silver nitrate is added to a solution, you conclude that the chloride ion is present. Which conclusion
    is more certain? Explain your answer.