Quiz 4 Flashcards
Precipitate was washed, then treated with 20 drops 6M NH4OH. All precipitate dissolves vs. Precipitate becomes black or grey.
Hg 2 2+
6M CH3COOH, 3-4 drops 1.5 K2CrO4 formation of yellow precipitate vs. No precipitate.
Pb2+
Filtrate is acidified by adding 6M HNO3 drop wise until a white precipitate reappears
Ag+
Add 1ml distilled water and 1ml 6M HNO3, heat and dark precipitate is present vs. Not present. Add Aqua Regia, divide into 2:
Half: 0.1M sncl2 a white precipitate forms.
Half: shiny liquid mercury on heavy copper wire
Hg 2+
To supernatant, add NH4OH. Dark blue ? White precipitate. Add sodium stannite. Turns black.
Bi3+
Blue solution. Add pinch na2s2o4 until dark precipitate forms. To other half, 6M acetic acid until acidic. Maroon precipitate appears
Cu2+
If solution is clear, 5 drops thioacetamide. Yellow precipitate. Or dark precipitate in which case HNO3 is added and repeat test.
Cd2+
Pale green precipitate, dissolve it in 6M NH4OH and add a few drops of C4H8O2N2. A red solution is present.
Ni 2+
To the supernatant, divide into 2 parts. Add 15 drops thioacetamide, white precipitate appears. Or a dark precipitate appears then add 1ml HCl. White or greyish precipitate forms.
To the other portion, acidify and precipitate turns white then dissolves when excess acid is added.
Zn2+
6M HCl, 2ml H2O and a few drops of KSCN. Appearance of dark blood red.
Fe2/3+
To the filtrate, add 6M HCl and 3M NH4OH. White precipitate.
Al3+
Solution is yellow, acidify with 6M HCl and a few drops H2O2. Appearance of dark blue complex.
Cr3+
Wash precipitate, then dissolve it in a few drops 3M HCl and 10 drops water. Add 4 drops 3M H2SO4. Formation of white precipitate.
Ba 2+
Add concentrated ammonia. Add several drops 0.25M ammonium oxaloacetate. A white precipitate forms.
Ca2+
Add 50mg na2HPO4. White crystalline precipitate forms
Mg2+
