Qualitative Analysis of an Unknown
Chemistry 1212L – Mondays 2:30-5:15 PM
October 18th, 2011
Block/McKelvy/Denniston/Silverstein (2008). Laboratory Experiments for Chem 1211L and 1212L. Cengage Learning, p 204-07 (Qualitative Analysis of an Unknown).
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 ...view middle of the document...
Remaining solution divided in two
5 drops of 0.2 M KSCN added to one portion
No formation of a blood-red solution occurred
This indicates that Fe3+ is absent
A few grains of NaBiO3 were added to other portion. No color change so it was heated in water bath
No formation of a pink or purple solution occurred
This indicates that Mn2+ is absent
Test wire cleaned with concentrated HCl
5 drop of the centrifugate from metal hydroxide test placed in tube, test wire dipped in solution
Loop of test wire brought to edge of outer cone of burner flame, at the height of the top of inner cone
Fleeting violet flame observed through cobalt blue glass
This indicates that K+ is present
No calculations occurred, only observations.
Unknown #723 contained: Silver (Ag+), Potassium (K+), and Nickel (Ni2+)
An area in this experiment where error could have occurred would be in
Being able to qualitatively analyze a solution to identify its contents is an important part of chemistry. Mixtures of ions in a solution can be separated by use of reagents to induce precipitation or color changes. This application has may uses in industry and research in todays world. This experiment covered the principles of complex ion equilibrium, solubility, oxidation reduction, and acid-base reactions. By applying these principles to the elements contained in an unknown solution, I was able to identify them as Silver (Ag+), Potassium (K+), and Nickel (Ni2+).