URDANETA CITY
UNIVERSITY
College of Pharmacy
Owned and operated by the City Government of Urdaneta
Laboratory Acti vit y no. 5
Separation of the Basic Constituents into Groups
Group I Cations
Objecti ves:
1. To be able to group the ions that f orm a precipitate with a part icular reagent.
2. Develop a systemat ic method to f acilitat e identif icat ion of ions
3. To Determine the dif f erent chemical r eaction pr inciples present in each
procedure
A. Separation of I Group cations ( Ag + , Pb 2 + , Hg
Nitrate forms
2+
) - Ag + , Pb 2 + , Hg
2+
are in the
Procedure
1 . Take 5 ml of a sample destined f or ident if icat ion and add 10 m l of 2M HCl.
You should obtain white precipitat e ( Precipitate A).
2 . Separ ate the precipitate by the f iltrat ion and wash it t wice with cold
dist illed wat er and discard the washing.
3 . Put clean test tube under the f unnel wit h the precipitate. Then wash the
precipit ate with 10 ml of hot distilled water and collect the supernatant
(Filtrate B). It is ver y important to remove all PbCl 2 f rom the precipit ate
to f ollow f urther analysis of remaining AgCl and Hg 2 Cl 2 which may be
present in the Preci pitate B
4 . Now you can conf irm the presence of Pb 2 + ions. In this pur pose divide the
solution of Filtrate B into three part and add KI, K 2 CrO 4 and H 2 SO 4 to
each test tube respectively. Addition of those chemicals successively will
yield a golden yellow precipitates of PbI 2 (reaction 4) and PbCrO 4
(reaction 5), and white precipitat e of PbSO 4 (reaction 6).
5 . Af ter conf irming the presence of Pb 2 + ions in the solut ion wash the
Precipitate B with addit ional portion of hot water unt il the washing give
no precipitate with K 2 CrO 4 solution.
6 . Pour ammonia solut ion onto the f ilter with Precipitate B and collect
colorless solution in cle an te s t t u be ( Filt rat e C ). O bs e rv e als o t h e f ilte r,
be c a u se t he pr e c ip it a te m a y d is so lv e com pletely or turn black. If the color
will change into black it means th at Hg 2 2 + is present in the init ial sample.
This is the f inal conf irmation of the Hg 2 2 + presence.
The lack of precipitat e indicate the absence of Hg 2 Cl 2 and the lack of Hg 2 2 +
cations in the initial sample. Theref ore, the last step is to f ollow the test
f or Ag + cations which is given below.
7 . Divide the Filtrate C into two parts. To the f irst one add dilute 2M nitric
acid HNO 3 (react ion 9). The f ormation of white precipitate of AgCl prove
the presence of silver. To the second test tube add the solut ion of
potassium iodide KI . Yellowish precipit ate of silver iodide AgI is the
additional conf irmation of the presence of silver ions in the sample
(reaction 10)
This document is not for sale and is solely for educational purposes of UCU pharmacy students only. Reproduction, distribution, uploading or posting online, trans mitting
in forms of any part of this document without prior permission is strictly prohibited.
URDANETA CITY
UNIVERSITY
College of Pharmacy
Owned and operated by the City Government of Urdaneta
8 . As you perf orm the expe riment, collect discard all in the appropriate waste
containers.
NOTE: DO NOT POUR ANY OF THE SOLUTIONS DOW N THE DRAI N.
D AT A AND RESULT:
1. Illustrate the schematic diagram f or group I Cations.
2. Give the chemical reaction f or each of the f ollowing steps.
3. W hat is the other name of group cations?
4. W hat are f lame tests? In what cat ion groups is this test used?
REFERENCES
This document is not for sale and is solely for educational purposes of UCU pharmacy students only. Reproduction, distribution, uploading or posting online, trans mitting
in forms of any part of this document without prior permission is strictly prohibited.