Analysis of an Unknown

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...