EXP 38: Qua. NH4+, Mg2+, Ca2+, Cu2+
➢ Experiment 38
· Skip parts A and B (NO FLAME TESTS)
· Only doing parts C-F
· Start warm/hot water bath in fume hoods incase needed later.
· Groups must grab one known/reference solution and one unknown (write letters down)
· ▪ One lab partner will do experiment with known/reference solution.
· ▪ Other partner will do experiment with unknown to compare with known.
· All blanks must be filled out excluding first two flame tests.
THE FOLLOWING PROCEDURE SHOULD BE DONE FOR BOTH REFERENCE AND THEN UNKNOWN.
TEST TUBES SHOULD BE HELD WITH TEST TUBE CLAMPS TO AVOID ACCIDENTAL SPILLING OF CHEMICALS ON STUDENTS WHILE HOLDING TEST TUBES.
Part C – Fume Hood
➢ 5 mL in a 100mL beaker on a wire gauze with Bunsen burner under and heat until moist residue (condensation starts) DON’T LET IT EVAPORATE COMPLETELY. Add 1-2 mL of D.I. Water
➢ Moisten a red litmus paper with water, add 1-2 mL of 6M NaOH to solution and suspend litmus above the solution. Litmus paper changing from red to blue confirms presence of NH4+
Part D – Fume Hood
Reducing Copper II ion
➢ 5 mL in a 150 mm test tube, polish 1 cm Zn strip (with steel wool) and place it into the solution. Let stand for 10-20 minutes. Decant solution and save for part E.1 DO NOT THROW AWAY
In our case, remove solution and leave behind the zinc (now copper metal with excess zinc). Can use pipette.
➢ Wash solid with a minimum of 3 portions of deionized water and disc...