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Date Submitted: 11/14/2011 09:23 AM
Qualitative Analysis of an Unknown
Chemistry 1212L – Mondays 2:30-5:15 PM
October 18th, 2011
Procedure:
Block/McKelvy/Denniston/Silverstein (2008). Laboratory Experiments for Chem 1211L and 1212L. Cengage Learning, p 204-07 (Qualitative Analysis of an Unknown).
Data:
Obtained unknown 723, light green in color.
1 drop of 12 M HCl added to 1-mL portion of unknown.
Precipitation occurred and no solid was initially present in unknown.
This indicates that the acid chloride group is present
Due to precipitation formation, additional HCl was added to test for complete precipitation
Test tube was centrifuged until no further precipitation was observed
1 mL of 6 M NH3 was added to the solid which remained after centrifugate was decanted, then stirred.
The solid did not turn gray
This indicates that Hg22+ is absent
6 M HNO3 added drop wise to ammonia until solution indicated acidity on litmus paper
Formation of a white precipitate occurred
This indicated that Ag+ is present
3 drops of 3 M H2SO4 added to centrifugate from original separation of acid chloride group
No precipitation occurred, and no solid was present in the original unknown.
This indicates that Ba2+ is absent
6 M NaOH added drop wise to centrifugate from separation of BaSO4 attempt until basic on litmus paper
Tube centrifugated and saved for subsequent tests to detect the Al3+ and K+ ions
1 mL of 6 M NH3 added to metal hydroxide precipitate and stirred then centrifuged, precipitate retained
3 M HC2H3O2 added to centrifugate until distinctive blue color of Cu(NH3)42+ and Ni(NH3)62+ destroyed
Acidified centrifugate divided into two portions
A few grains of NaCl added to one portion, iron nail lightly sanded and placed in acidified centrifugate
No formation of a brown coating on the nail occurred
This indicated that Cu2+ is absent
A few grains of DMG was added to the other portion of the acidified centrifugate
A formation of red precipitate occurred
This...