Objective: To correctly identify cations and anions in a series of solutions.
1. Each team will be given ten solutions, each of which contains a single pure salt. The anion will be one of the following: carbonate, sulfate, chloride, acetate, or iodide. The cation will be one of these: ammonium, sodium, potassium, barium, or lithium. Thus, there are 25 possible salts.
2. The identity of the salts will be determined from the following chemical tests. All of the necessary chemicals will be provided.
3. The maximum allowed working time is 30.00 minutes.
Test for Cations:
A. Test for metallic cations. Use the flame test to identify metallic cations:
Na+ yellow
K+ purple (faint)
Ba+2 green
Li+ red
NH4+ no color-See Test B
B.
Test for ammonium: Add 1 mL of 6 M NaOH to about 1 mL of your
unknown
solution. A faint ammonia odor should be detected if NH4+ is the
cation.
Moistened litmus paper can also be used to check for the presence of
ammonia
(red litmus turns blue).
Test for Anions:
C. Test for Carbonate: Cautiously add 1 mL of 6 M HCl to 1 mL of your unknown. Odorless bubbles will be noted if carbonate is present.
D. Test for Sulfate: Add 1 mL of 6 M HCl to 1 mL of your unknown. Next add a few drops of 1 M BaCl2. A white, finely divided precipitate indicates the presence of the sulfate ion.
E. Test for Iodide: Add 1 mL of starch solution to 1 mL of your unknown solution. Next add 1 mL of the dilute H2O2 solution. A blue color is indicative of the presence of iodide.
F. Test for Chloride: Add 1 mL of 6 M HNO3 to 1 mL of your unknown solution. Next add a few drops of 0.1 M AgNO3. A white precipitate confirms the presence of chloride.
G. Test for Acetate: Add 1 mL of 3 M H2SO4 to 1 mL of your unknown solution and stir. A vinegar odor is indicative of acetate. Moist litmus paper can also be used to check for the presence of acetic acid (blue litmus turns red).
3. Your score will be awarded as follows: From 110 points, your team score will be deducted (a) four points for every incorrectly identified ion plus 1 point for every minute that it takes to complete the event (start time is receipt of solutions; finish time is submission of answer sheet). For example, if a team finishes in 22 minutes with three (out of 20) ions incorrectly identifies, the team score will be 110 ? 12 ? 22 = 76.
4. Safety glasses must be worn at all times!
5. General safety in handling of chemicals must be exercised at all times. The Quick Qual officials may disqualify an individual for conduct and safety violations.
