ASSUMPTION UNIVERSITY
FACULTY OF ENGINEERING
BASIC SCIENCE DEPARTMENT
CHEMISTRY LABORATORY REPORT
BG 14032 GENERAL CHEMISTRY LABORATORY
EXPERIMENT (10)
Cation Analysis Group (III)
Submitted to:
: A.
Kyi Kyi Tin
Submitted by:
: Mr. Si Thu Tun (ID 6218135)
Section
:642
Date(4/4 / 2020)
Semester (2/2019)
I. Purpose of the experiment
The purpose of inorganic qualitative analysis is to enable
- The acquisition of powers of observation and deduction
- The learning of reaction of inorganic chemistry
- The development of practical chemical skills
II. Introduction
In many real situation, a chemist must gather observation to decide the chemical identity of an
unknown sample. Given a totally “unknown” sample, how does go about determining what is
actually present? This process is called “qualitative analysis” .
Cations are classified into five groups on the basis of their behavior against some reagents by
using groups reagents; we can decide presence or absence of groups of cations and can also
separate these groups for further examination.
The group reagents used for the classification of most common cations are hydrochloric
acid, hydrogen sulphide , ammonium sulphide and ammonium carbonate.
Classification is based on whether a cation reacts with these reagents by the formation
of precipitates or not. Therefore, it can be said that classification of most common
cations is based on the differences of solubilities of their chlorides. Sulphides and
carbonates.
The five groups are as follows:
Group I… Cations from precipitates with dilute hydrochloric acid.
Ions of this group are
Lead Mercury(I), and Silver
Group II. Cations do not react with hydrochloric acid, but from precipitates with
hydrogen sulphide in dilute mineral acid medium.
II A. Mercury (II), Copper , Bismuth, Cadmium Sulphides of II A are insouluble in (NH4)2S
II B. Arsenic (III), Arsenic (V), Antimony (III), Antimony (V), Tin(II) and Tin(IV). Sulphides
of II B are soluble in (NH4)2S.
Group III Cations do not react either with dilute mineral acid medium.
They form precipitates with ammonium sulphide in neutral or ammonical media.
They are Cobalt(II), Nickel (II), Iron (II) Iron(III), Chromium (III), Aluminum, Zinc , and
Mangenese(II).
Group IV Cations do not react with the reagents of group I, II and III. They form
precipitates with Ammonium carbonate in the presences of ammonium chloride in
neutral or slightly acidic media
Group V. Cations do not react with reagents of previous groups.
They are Magnesium, Sodium, Potassium, Ammonium, Lithium, and Hydrogen ions.
III. Experimental
3.1 Chemicals
3.2 Equipment
3.3 Procedure
Take 5ml known solution sample in the test tube and follow instructions accordingly,
and report your results in the table given below:
Fe(III) ion
Reagent
1(a).Add NH3 soln.
Al(III)ion
Reddish brown ppt
White jelly ppt
insoluble
Insoluble
Reddish brown ppt
White jelly ppt
insoluble
soluble
(NH4OH) 1-2 drops
(b) excess NH3
soln.
2(a). Add NaOH soln. 1-2
drops
(b) excess NaOH soln.
3. Add K4Fe(CN)6 soln. to
Fe(III) ion sol
4. Add KSCN soln. to Fe
n.
(III) ion soll
Deep blue
n.
Blood Red
Equation
FeCl (aq) + 3NH OH(aq)
3
3NH Cl(aq)+ Fe(OH) (s)
4
4
3
AlCl (aq) + 3NH OH(aq)
NH Cl(aq) + Al(OH) (aq
Fe(OH)3aq) + 3HCL(aq)
FeCl3(aq) + 3NaCl(aq)
3
4
4
Al(OH) (aq) + 3HCl(aq)
FeCl (aq) + 3NaOH(aq)
Fe(OH)3(aq) + 3NaCl(aq)
3
3
3
2
FeCl3(aq) + 3H2O(l)
Remark
Group III cation
present
Reddish Brown ppt
Clear solution
Fe(OH)3, Al(OH)3
Group II to V ions
Black brown ppt was
formed
Fe(OH)3 and
(NaAlO2)
Brown ppt
Clear solution
Fe(OH)3
NaAlO2
Residue II (Fe(OH3)was
dissolved in minium volume of
dil HCl sol and divided into two
tube.
KCNS solution was added to first
tube with Fe(OH)3
Blood red suspension
[Fe(SCN)3
Confirmed presence
of Fe3
K Fe(CN)6]3 solution was added
to second test tube with Fe(OH)3
Deep blue suspension
(Fe4[Fe(CN)6]3
Confirmed presence
of Fe3+
NH Cl solution was added
to Filtrate II than stirred well
and boiled.
White suspension
Al(OH)3
Co(N03)2 was added
Blue suspension
Confirmed presence
of Al3+
n
3NaCl(aq)+2H2O(l)+NaAlO (aq)
Fe(OH) (aq) + 3HCL(aq)
observation
Reddish brown ppt was
formed
Reddish Brown ppt. was washed
with a small amount of distilled
water and dissolved in minimum
volume of dil HCL
NaOH sol was added and boiled
in hot water and filtered during
hot.
Residue II
Filtrate II
AlCl3(aq) + 2H2O(l)
3
AlCl (aq)+4NaOH(aq)
3
No Experiment
1
NH4Cl and NH4OH was added to
mixture, than stirred ,boiled and
filtered
Residue I
Filtrate I
3
n
FeCl (aq) + 3KCNS(aq)
3
4FeCl3(aq) + 3K4Fe(CN)6 (aq)
12KCl(aq)
Fe(CNS)3(aq) + 3KCl(aq)
Fe[Fe(Cn)6]3(aq) +
NaAlO2(aq) + NH4Cl(aq) + H2O(l)
NaCl(aq) +
NH3(g) + Al(OH)3(s)
2Al(OH)3(s)
3H2O(l) + Al2O3(s)
Al2O3(s)
O2(g)
+ 2Co(N03)2(aq)
2CoAl2O4(s) + 4NO2(g) +
4
4
4
IV. Results and discussions
The given unknown salt mixture solution is found to be Cation Group(I)
(i) Fe(III) ion is confirmed
(ii) Al(III) ion is confirmed
V. Conclusion
The given unknown salt mixture solution is found to be Fe(III) ion and Al(III
Form cation Group(III)