INTRODUCTION TO THE CHEMISTRY LABORATORY

Laboratory is a place, usually a room where scientific research or experiment are carried out by the use
of pieces of apparatus and chemical reagents.

GENERAL LABORATORY SAFETY RULES

1. Do not enter laboratory without the direct supervision of the teacher

2. Do not remove materials from the laboratory except when instructed to do so by the
teacher
3. Before beginning an experiment, ensure that you know the principle behind all the steps
in the procedure
4. Clean all the apparatus after use and return them to their proper place
5. Ensure that you clean your bench after the experiment
6. Use the minimum amount of chemicals unless instructed otherwise
7. Do not eat, play or fight in the laboratory
8. Wash your hands before and after the experiment
9. Report any accidents immediately to your instructor
10. You are not allow to enter the laboratory without putting on laboratory coat
GENERAL SAFETY PRECAUSION
1. Never taste a chemical unless instructed to do so. If accidentally a chemical get into your
mouth, spit it out immediately and wash your mouth thoroughly with water
2. When instructed to smell a chemical or gas, do so by fanning the vapour or gas gently
with your palm toward your nose
3. Handle all glassware with care to avoid glass cuts
4. When any chemical get to your skin, wash the affected part with plenty of water, remove
clothing from the affected part.
5. In case of inhalation of poisonous gas, move out into open air
6. When poisonous chemical is swallowed, drink large amount of water to induce vomiting;
seek medical help
7. When chemical get into your eyes, wash the eyes with plenty of water. Lie down if
necessary and medical treatment immediately

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 CHAPTER ONE

INTRODUCTION TO QUALITATIVE INORGANIC ANALYSIS

Qualitative inorganic analysis is a technique being used for the detection of the elements, in the
form of cations (metallic ions) and anions (acid radicals) present in inorganic compounds.

Laboratory Experiments in Qualitative analysis

Laboratory experiments in qualitative analysis involve performing series of tests, making

necessary observations, and arriving at logical conclusion.

Laboratory test: What to be done. It may be physical or chemical:

 A physical test involves identifying the state of a substance, its colour, odour and
solubility in water.
 A chemical test involves action of heat on a substance, action of substance on a test paper
and addition of bench reagent to the substance.

Observation: what you see (colour change, effervescence, bubbles, etc), smell/odour (choking,
pungent, irritating, rotten egg, sweet, pleasant etc), hear (pop sound, hissing sound, cracking
sound etc) feel (test tube or container becomes cold or warm)

Inference (Conclusion): Logical deduction(s) from the observation(s)

Stages for the Identification of Ions

The main stages in the identification of ions are as follows:

1. Preliminary test
2. Test for anions
3. Test for cations

Preliminary test

Preliminary tests involves the physical properties (e.g. appearance, smell, colour), action of heat,
solubility and flame test.

Physical Properties

Note the appearance, colour and smell of the unknown sample

Observe the colour, and examine if the substance is crystalline or powdwery;

 If the substance is powdery, then, it is anhydrous; if it is crystalline, then, it may be

hydrated

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  If the substance is white, and its solution in water is colourless, then transition metal ion
is absent
 If the substance is white or coloured, and its solution in water is coloured, transition
metal ion present

The characteristic colours of some metal ions in solid state, or in aqueous solutions are as
Colour Cation follows
Blue or Green Copper (II), Cu2+
Brown or Yellow Iron(III), Fe3+
Pale green Iron(II), Fe2+
Black CuO or C
Smell of ammonia Ammonium salt

Solubility of Salts in Water

 All sodium, potassium and ammonium salts are soluble in water

 All trioxonitrate(V) salts, NO3- are soluble in water
 All chlorides, Cl- are soluble in water, except those of Ag, Pb and Hg(II).
 All tetraoxosulphate(VI) salts, SO42- are soluble, except those of Pb, Ba. CuSO4 is slightly
soluble in water
 All tetraoxosulphate(IV) salts, SO32- are insoluble, except those of sodium, potassium and
ammonium salts which are insoluble in water.
 All trioxocarbonate(IV), CO32- are insoluble, except those of sodium, potassium and
ammonium salts which are insoluble in water.
 All sulphides, S2- are insoluble, except those of sodium, potassium, ammonium salts,
calcium, magnesium and barium salts which are insoluble in water.

Flame Test

Some metals and their cations can be identified from the characteristic colours their salts impart
to a non-luminous Bunsen burner flame.

Place the sample on a dry spatula or platinum wire, and heat on a non-luminous Bunsen burner
flame:

Colour Inference
a. Brilliant or golden yellow Sodium ion, Na+
b. Lilac Potassium ion, K+
c. Brick-red Calcium ions, Ca2+
Action of Heat on a
d. Bluish green or dark green Copper (II) ions, Cu2+
Solid Sample (Dry Test)
e. Pale or light blue Lead (II) ions, Pb2+
f. Yellowish green Barium ions, Ba2+ 3
When solid sample is heated, observe if it melts with or without loss of water vapour; sublimes,
leaving no residue; decomposes leaving a residue; the heat has no effect on the solid. Note
changes in colour

The solid ids heated in a dry test tube over a Bunsen burner flame; first gently, then, strongly:

Observation Inference
a. Melts; vapour condenses on the upper or Salt is hydrated
cooler part of the test tube
b. White sublimate formed Ammonium ion, NH3+ present
c. Cracking sound with decomposition Salt is Pb(NO3)
Cracking sound without decomposition Salt is NaCl
d. Change in colour on gentle heating
 Blue to white  CuSO4.5H2O
 Green to brown  CuCl2.2H2O
 Pale green to white  FeSO4.7H2O
 Yellow to black  FeCl3
e. Colour of residue on strong heating
 Yellow when hot, white when cold  Residue ZnO, from ZnCO3 or
Zn(NO3)2
 Red when hot, yellow when cold  Residue PbO, from PbCO3 or
Pb(NO3)2
 Black when hot and cold  Residue CuO, from CuCO3 or
Cu(NO3)2

CHAPTER TWO

IDENTIFICATION OF CATIONS

Wet test: In a wet test, an aqueous solution of the solid sample is made in distilled water. An
appropriate reagent is then added to the solution of the sample, in order to order to precipitate an
insoluble compound that has a characteristic colour, or cause oxidation or reduction.

Cations are classified into two on the basis of their colours in aqueous solutions:

1. Colourless: Ca2+, Pb2+, Zn2+, Al3+ and NH4+

2. Coloured: Cu2+ (light blue), Fe2+ (dirty green) and Fe3+ (brown)
The reagents that are used in identifying cations in separate aqueous solutions are: first sodium
hydroxide, NaOH solution, and then, ammonia, NH3 solution.
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The reagents are added into a fresh solution of the substance; first, in drops (2 or 3 drops), then,
in excess (5 or more drops).
Experimentally, two types of are precipitates are produced when NaOH(aq) and NH3(aq) are used as
precipitating agents.
 Gelatinous precipitate is very light and jelly-like; it does not settles down on standing.
 Chalky or non-gelatinous precipitate is heavy; it settles down readily on standing.
Use of NaOH solution
Put 2cm3 of the solution of sample in a test tube, add NaOH(aq) in drops, then, in excess and
shake:

Observation Inference
a. White chalky precipitate, insoluble in excess NaOH Ca2+ present
solution
b. White chalky precipitate soluble in excess NaOH solution Pb2+ present
c. White gelatinous precipitate soluble in excess NaOH Zn2+ or Al3+ present
solution
d. Light blue gelatinous precipitate insoluble in excess Cu2+ present
NaOH solution
e. Dirty green gelatinous precipitate insoluble in excess Fe2+ present
NaOH solution
f. Brown gelatinous precipitate insoluble in excess NaOH Fe3+ present
solution
g. No precipitate or no visible reaction. On heating the Gas is alkaline;
mixture, gas given off is colourless, with choking smell, Gas is NH3 from
the gas turns red litmus blue, and form dense white fumes NH4 salt
with vapour of concentrated HCl.

Use of NH3 Solution

Put 2cm3 of the solution of sample in a test tube, add NaOH(aq) in drops, then, in excess and
shake:

Observation Inference
2+
a. No precipitate or no visible reaction Ca present
b. White chalky precipitate insoluble in excess NH3 solution Pb2+ present
c. White gelatinous precipitate soluble in excess NH3 Zn2+ present
solution
d. Light blue gelatinous precipitate soluble in excess NH3 Cu2+ present
solution to give a deep blue solution
e. White gelatinous precipitate insoluble in excess NH3 Al3+ present
solution
f. Dirty green gelatinous precipitate insoluble in excess Fe2+ present
NH3 solution
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 g. Brown gelatinous precipitate insoluble in excess NH3 Fe3+ present
solution

Confirmatory Test for Cations

Except the test for ammonium ion, the following are the additional tests that can be performed to
confirm the presence of some cations.

Calcium ion, Ca2+

To the solution, add dilute H2SO4 solution
The solution turns milky, and later gives a white precipitate

Zinc ion, Zn2+

To the solution, of the substance, few drops of ammonia solution, then add ammonium chloride
solution
A white precipitate confirms the presence of zinc ion

Lead(II) ion, Pb2+

i. To the solution of the substance, add few drops of dilute HCl.
A white precipitate which dissolves on heating and reappear on cooling confirm Pb2+
[This test can be used to distinguish between Pb2+ and Al3+ in a solution. Al3+ does not
form precipitate with HCl.
ii. Add few drops of potassium iodide solution to the solution of the substance.
A bright yellow precipitate confirms Pb2+
iii. Add few drops of potassium tetraoxochromate(VI) solution to the solution of the sample.
A yellow precipitate conforms Pb2+
iv. To the solution of the substance, add few drops of dilute H2SO4 solution.
A white precipitate confirms Pb2+

Copper(II) ion, Cu2+

i. To the solution of the sample, add excess ammonia solution.
A deep blue solution confirms Cu2+
ii. To the solution of the substance, add potassium iodide solution.
A brown solution and a dirty white precipitate, confirms the presence of Cu2+

Iron(II) ion, Fe2+

i. Add few drops of HNO3 to the solution of the sample and boil for a while.
The solution turns brown, Fe2+ oxidized to Fe3+
ii. Add few drops of acidified KMnO4 solution to the solution of the sample.
Purple colour of KMnO4 decolourrised. Fe2+ is reducing agent
Iron(II) ion, Fe3+
To the solution of the substance, add a few drops of potassium thiocyanate solution, KSCN(aq)

6
 CHAPTER THREE
IDENTIFICATION OF GASES
Gases are given off when certain substances are heated separately, or when a dilute mineral acid,
such as HCl or H2SO4 solution is added to such substances.
Classification of Gases
Gases can be classified into three groups as follows:
1. Acidic gases
2. Alkaline (basic) gases
3. Neutral gases
General Method of Identifying Gases
Gases can be identified by the following methods or tests:
 Colour recognition
 Odour or smell of the gas
 Action of the gas on moist red or blue litmus paper
 Laboratory confirmatory test

Identification of Gases by Colour Recognition

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Most common gases are colourless, while only a few have characteristics colour. For instance,
CO2, SO2, HCl, H2S, H2O and O2 are all colourles. NO2 and Br2reddish-brown, Cl2 is a greenish-
yellow gas; while I2 is violet or purple.

Identification of Gases by Odour Detection

Most gases are poisonous, and so, it is advisable that as much as possible they should not be
inhaled. A few gases have their characteristic odour, while other are oduless.

Identification of Gases by the Use of Litmus Paper

There are two types of litmus papers; the blue and the red litmus papers. The reactions between
these papers and the gases are as follows:
a. Acidic gases turns moist blue litmus paper red; they have no effect on the red litmus paper
e.g CO2, SO2, HCl, H2S, and NO2.
b. Alkaline gases turn moist red litmus paper blue; they have no effect on the blue litmus
paper e.g ammonia, NH3, which is the common alkaline gas known.
c. Neutral gases have no effect on both the red abd blue litmus papers e.g CO, and H2O.

The table below gives a summary of the characteristic physical properties of common gases.
Tests using litmus papers is chemical tests.

GAS COLOUR AND ACTION ON MOIST LITMUS

ODOUR
a. Carbon(IV) oxide, CO2 Colourless and odouless Turns blue litmus red; acidic
b. Sulphur(IV) oxide, SO2 Colouless and pungent Turns blue litmus red; acidic
c. Hydrogen sulphide, Colouless and rotten- Turns blue litmus red; acidic
H2S egg
d. Nitrogen(IV) oxide, Brown and pungent Turns blue litmus red; acidic
NO2
e. Hydrogen chloride, Colouless and pungent Turns blue litmus red; acidic
HCl
f. Chlorine, Cl2 Greenish-yellow and Turns blue litmus red; acidic
pungent
g. Bromine, Br2 Reddish-brown and Turns blue litmus red; acidic
pungent
h. Iodine, I2 Violet or purple and Turns blue litmus red; acidic
pungent
i. Ammonia, NH3 Colourless and choking Turns red litmus blue; alkaline
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 j. Hydrogen, H2 Colourless and No action on litmus paper
odourless
k. Oxygen, O2 Colourless and No action on litmus paper
odourless
l. Water vapour, H2O Colourless and No action on litmus paper
odourless

Confirmatory Test for Gases

Carbon(IV) oxide, CO2
Allow the gas to come in contact with lime-water on a glass rod.
Gas turns lime water milky.
NOTE: when the gas is passed into limewater for a long time the milkness disappear, due to the
formation of Ca(HCO3)2.

Sulphur(IV) oxide, SO2

i. Insert a strip of filter paper soaked into KMnO4 solution into the gas.

The gas decolourizes the purple colour of KMnO4.

ii. Insert a strip of filter paper soaked into K2Cr2O4 solution into the gas.

Gas turns the yellow colour of K2Cr2O4 to green. SO2 is a reducing agent

Hydrogen sulphide, H2S

Insert a strip of filter paper soaked into KMnO4 solution into the gas.

The gas decolourizes the purple colour of KMnO4 and form a yellow deposit of Sulphur

Nitrogen(IV) oxide, NO2

Introduce a moist starch-iodine paper into the gas.

The paper turns blue-black, due to the liberation of iodine gas, which then combined with starch.
NO2 is an oxidizing agent.

Chlorine, Cl2

Introduce a moist starch-iodine paper into the gas.

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The paper turns blue-black, due to the liberation of iodine gas, which then combined with starch.
Cl2 is an oxidizing agent.

Hydrogen chloride, HCl

Allow the gas to come in contact with a strip of filter paper soaked in concentrated ammonia
solution.

A dense white fume of ammonium chloride is formed.

Ammonia, NH3

Allow the gas to come in contact with a glass rod dipped into concentrated hydrochloric acid.

A dense white fume of ammonium chloride is formed.

Hydrogen, H2

Introduce a lighted splint into the gas.

The gas burns with a characteristic pop sound, due to the violet combination with oxygen in air

Oxygen, O2

Introduce a glowing splint into the gas.

The glowing splint relights or rekindles, oxygen support combustion

Water vapour, H2O

i. Allow the gas to come in contact with white anhydrous CuSO4 powder on spatula
The gas turns the white powder to blue
ii. Allow the gas to come in contact with blue anhydrous cobalt(II) chloride on a spatula
The gas turns the blue powder pink.

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 CHAPTER FOUR

IDENTIFICATION OF ANIONS (ACID RADICALS)

Anions are negatively charged ions. Examples, NO3-, SO42-, CO32-, SO32- e.t.c
Methods of Identification of Anions
The anions in an inorganic salt can be identified by the following methods:
Dry Tests: In a dry test, the solid sample is heated alone, or an aqueous acid is added directly to
the solid sample, in order to produce a gas that can be readily identified. The identity of the gas
provides useful information about the anion present in the given sample. The dry test is done
through the following:

Action of Heat on a Solid Sample

Test: Put a spatulaful of the solid sample in a clean dry test tube. Heat gently first, then strongly.
Note the evolution of any gas, melting, temporary or permanent colour change. Draw any
inference.

S/ Observation Inference
N
1. If brisk effervescence occur, colourles and odouless The gas is acidic, gas is CO 2
gas evolved which turns blue litmus red and turns lime from CO32- or HCO3-
water milky
2. If colourless gas evolved with a pungent smell; which Gas is SO2 from SO32-, S2O32- or
turns wet blue litmus paper red and decolourizes SO42-
acidified KMnO4 on a strip of filter paper
3. If reddish-brown gas evolved with pungent smell, Gas is NO2 from NO2- or NO3-
turns blue litmus paper red, and turns starch-iodine (except those of alkali metals)
paper blue-black
4. If on heating with MnO2, the gas evolved is greenish- Gas is chlorine, Cl2 from Cl-
yellow with pungent smell, which turns blue litmus
paper red and bleached it.
5. If colourless gas evolved with a choking smell, which Gas is NH3 from NH4+
turns moist red litmus paper to or a white sublimate is
observed
6. If water vapour condenses on the upper or cooler part Salt is hydrated, or from HCO3-
of the test tube.
7. If colourless and odourless gas evolved which has no Gas is oxygen, O2 from NO3- of
effect on litmus papers, and rekindles a glowing splint alkali metals
is observed.

Action of Dilute HCl on a Solid Sample

11
Test: Put a spatulaful of the solid sample in a clean test tube and add several drops of dilute HCl.
Warm, if there is no reaction. Note the evolution of any gases evolved.

The following observations and inferences can be drawn from different substances

S/ Observation Inference
N
1. If brisk effervescence occur, colourles and odouless The gas is acidic, gas is CO 2
gas evolved which turns blue litmus red and turns lime from CO32- or HCO3-
water milky
2. If effervescence occur, colourless gas evolved with a Gas is acidic; gas is SO2 from
smell of burning Sulphur or irritating smell; which SO32-
turns wet blue litmus paper red and decolourizes
acidified KMnO4 on a strip of filter paper or yellow
solution of K2Cr2O4 turns green
3. If reddish-brown gas evolved with pungent smell, Gas is NO2 from NO2-
turns blue litmus paper red, and turns starch-iodine
paper blue-black
4. If effervescence occur, colourless gas evolved with Gas is SO2 from S2O32-
rotten egg smell, which turns moist blue litmus paper
red and decoulourizes KMnO4 with a yellow deposit
of Sulphur (solid).
5. If effervescence occur, colourless gas evolved with Gas is H2S from S-
rotten egg smell, which turns moist blue litmus paper
red and turns lead(II) ethanoate paper black
6. If there is no visible reaction, no gas evolved, even on Cl-, Br-, NO3- or SO42- present
warming.

Action of concentrated H2SO4 on a Solid Sample

Test: Put a spatulaful of the solid sample in a clean dry test tube and add few drops of conc.
H2SO4 with care.observe the any reaction; then warm carefully, but do not heat strongly.

NOTE: The reactions of CO32, HCO3-, S2O32-, SO32-, NO2-, and S- with conc. H2SO4 are exactly
the same with dilute HCl discussed above, but the reaction with conc. H2SO4 are more vigorous,
and cannot be used to confirm these radicals.

S/ Observation Inference
N
1. If colourles gas evolved with pungent smell, which The gas is HCl from Cl-
turns wet blue litmus paper red and forms dense white
fumes of ammonia solution on a glass rod.
2. If reddish-brown gas evolved with pungent smell, Gas is HBr from Br-
which turns wet blue litmus paper red and forms dense
white fumes of ammonia solution on a glass rod.
3. If violet or purple gas evolved with pungent smell, Gas is HI from I-
turns blue litmus paper red, and turns starch-iodine

12
 paper blue-black
4. If reddish-brown gas evolved with pungent smell, Gas is NO2 from NO2- or NO3-
which turns wet blue litmus paper red, and turns
starch-iodine paper blue-black
5. If there is no visible reaction, no gas evolved. SO42- present

Wet Tests: In wet tests, an aqueous solution of the solid sample is made in distilled water. An
appropriate precipitating reagent is then added to the solution of the sample, so as to precipitate
an insoluble compound that has a characteristic colour, or to cause oxidation or reduction.

Uses of Some Common Laboratory Bench Reagents

Reagent Anion precipitated

a. AgNO3 solution CO32-, SO32-, S-, Cl-, Br-, or I2
b. BaCl2 solution CO32-, SO32-, S- or SO42-
c. Acidified KMnO4 Oxidation of SO32- or S-
solution
d. Pb(NO3)2 solution CO32-, SO32-, S-, SO42-, Cl-, Br-,
or I2

Use of Silver Trioxonitrate(V), AgNO3 solution

Test: To the solution of the sample in a test tube, add few drops of AgNO3 solution

Observation and Inference

a. A white precipitate, soluble in excess dilute HNO3. CO32-or SO32- present

b. A white precipitate, insoluble in excess dilute HNO3. Cl- present
c. A yellow-white precipitate, insoluble in HNO3. Br- present
d. A yellow precipitate, insoluble in HNO3. I- present
e. No visible reaction or no precipitate, indicates the absence of CO32-, SO32-, S- and the
halides

Use of Barium Chloride, BaCl2 Solution

Test: To the solution of the sample in a test tube, add few drops of BaCl2 solution
Observation and Inference
a. A white precipitate, soluble in excess dilute HCl. CO32-, S- or SO32- present
b. A white precipitate, soluble in excess dilute HCl. SO42-
c. No visible reaction or no precipitate, indicates the absence of CO32-, SO32-, S- and SO42-

NOTE: Ba(NO3)2 and dilute HNO2 can be used in place of BaCl2 and HCl.

Use of Lead(II) Trioxonitrate(V) Solution

13
Test: To the solution of the sample in a test tube, add few drops of solution Pb(NO3)2 solution.

Observation and Inference

a. A white precipitate that dissolves on warming and reappear on cooling confirm Cl- in the
solution
b. A white precipitate insoluble on heating shows the presence of CO32-, SO32- or SO42-
c. No visible reaction or no precipitate, indicates the absence of CO32-, SO32-, S- and SO42-
and Cl-
NOTE: Pb(NO3)2 can be used in place of Pb(CH3COO)2 solution

Use of Acidified KMnO4 solution

Test: To the solution of the sample in a test tube, add 2 or 3 drops H2SO4 and add KMnO4
solution dropwise.
Observation and Inference
a. If there is immediate decolourization of the purple colour of KMnO4 solution, then,
reducing agent such as SO32- is present.
b. If there is no colour change, then, a reducing agent is absent

Confirmatory Test for Anions in Aqueous Solution

Halide (Cl-, Br- and I-)
Test: To the solution of the sample, add few drops of HNO3, followed by a few drops of AgNO3
solution
 A white precipitate which is soluble in ammonia solution, confirms the presence of Cl-
 A creamy white precipitate which is slightly soluble in ammonia solution, confirms the
presence of Br-.
 A pale yellow precipitate which is insoluble in ammonia solution, confirms the presence of
I-.
NOTE: The solution of the sample is first acidified with dilute HNO3 before the addition of
AgNO3, in order to remove interfering ions such as CO32-, SO32-and S- that also form white
precipitate with AgNO3 solution.

Tetraoxosulphate(VI) ion, SO42-

Test: To the solution of the sample, add few drops of HCl, followed by BaCl2 solution.
A white precipitate, insoluble in dilute HCl, confirms SO42-.
NOTE: The solution of the sample is first acidified with dilute HCl before the addition of BaCl2,
in order to remove interfering ions such as CO32-, SO32-and S- that also form white precipitate with
BaCl2 solution.

Trioxosulphate(IV) ion, SO32-

Test 1: To the solution of the sample, add few drops of HCl, followed by BaCl2 solution.
A white precipitate, soluble in dilute HCl, confirms SO32-.
Test 2: To the solution of the sample, add few drops of acidified KMnO4. Purple colour of
acidified KMnO4 solution decolourized. SO32- Is a reducing agent.
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Sulphides ion, S-
Test 1: To the solution of the sample in a test tube, add few drops of solution lead(II) ethanoate
solution Pb(CH3COO)2 solution. A black precipitate comfirms S-.
Test 2: To the solution of the sample, add few drops of acidified KMnO4. Purple colour of
acidified KMnO4 solution decolourized with a deposit of yellow sulphur. S- Is a reducing agent.

Trioxonitrate(V), NO3-
Test: To the solution of the sample, add few drops of freshly prepared FeSO4 solution, followed
by concentrated H2SO4 along the side of the test tube, with the test tube in slanting position.
A brown-ring is formed in between the acid (below) and the solution (above).

Trioxocarbonate(IV) ion, CO32-

Test 1: To the solution of the sample, add BaCl2 solution.
A white precipitate, soluble in dilute HCl, confirms CO32-.
Test 2: To the solution of the sample, add few drops of phenolphthalein indicator.
The solution turns pink; solution is alkaline.

CHAPTER FIVE
QUALITATIVE ORGANIC ANALYSIS
This involves the techniques employed in the identification of the various elements and functional
groups present in organic compounds. The techniques generally employed include: action of heat
on the substances, solubility in various solvents and the action of reagents on the substances.
TEST FOR FUNCTIONAL GROUPS
Test for unsaturation
a. With bromine water: to a little of the unknown substance, add a few drops of bromine
water. If there is immediate decolourization in the cold then the compound is saturated.
b. With KMnO4: To the solution of the unknown substance, add a few drops of KMnO4. If
the purple colour of KMnO4 is decolourized, then the compound is unsaturated
Test of alkanols
To a little amount of substance, add 2cm3 of ethanoic acid, and a few drops of H2SO4. Boil with
care for a while. An ester is formed with a characteristic of pleasant fruit smell. This indicate the
presence of alkanol.
Test of alkanoic acid
To a little amount of substance, add 2cm3 of NaHCO3 or KHCO3 solution. If there is
effervescence and a colourless and odorless gas which is acidic to litmus and turns lime water
milky is given off. The gas is CO2 and the substance is an alkanoic acid.
Test for Reducing Sugar
a. Using Fehling’s solution: To the solution of the substance in a test tube, add 1cm3
Fehling’s solution, and boil for a while. A reddish brown precipitate indicate the presence
of reducing sugar such as glucose, fructose, maltose or galactose

15
 b. Using Benedic solution: To the solution of the substance, add 1cm3 of Benedict solution.
If the solution changes from blue to green and a yellow, orange or reddish-brown
precipitate is formed, then a reducing sugar is present.
Test for Starch
To the solution of the substance in water, add a few drops of iodine solution. If the solution turns
blue-black, then it contains starch.
Test for Protein (Amino Acids)
a. Biuret Test: To the solution of the substance in a test tube, add few a drops of NaOH and
swirl briefly. Then add a few drops of CuSO4 solution and swirl the mixture. A purple
colouration shows the presence of amino acid/protein
b. Millon’s Test: (Millon’s reagent is a mixture of mercury and conc. HNO3). To the
solution of the substance in a test tube, add a few drops of Millon’s reagent and warm. A
white precipitate which turns red after a while shows the presence of an amino
acid/protein.
c. Xanthoproteic Test: To a little solution of the substance in a test tube, add conc. HNO3
and warm. A yellow colouration confirms the presence of an amino acid/protein.
d.

CHAPTER FIVE

WRITING REPORT OF TESTS ON QUALITATIVE ANALYSIS

Laboratory work performed in qualitative analysis is recorded in tabular form with the heading:
Test; Observation; Inference. The following should be noted when writing report of test on
qualitative analysis

1. Report should be written clearly and briefly with avoidance of ambiguity.

2. When a test is performed, the observations and hence, the inferences should be written
immediately, in order not to forget part of the observation.
3. When reporting any test performed, the observations and inferences must correspond, in
order to prevent mix-ups.
4. Always check the label on the bench reagent bottlebefore using it; to avoid using wrong
reagent.
5. The correct name of the reagent used must be written in the test performed. If NaOH(aq)
is used in a test, and NH3(aq) is written down in the report, it is a wrong test; observation
and inferences will be considered wrong.
6. If there is colour change on heating a solid sample, note the colour change; a gas may be
given off.
7. When a solid sample dissolved in water, the solution obtained can be colourless or
coloured; but not white or gelatinous.
8. When the original substance provide is a solid, and a test performed on the solution of the
sample, report should be written to show that the solution of the sample has been used.

16
 9. When precipitating reagent is added to a solution in drops, note whether a precipitate is
formed or not; then, record your observation and the appropriate inference. When the
reagent is now added in excess, note whether precipitate dissolves or not; then, record
your observation and the appropriate inference.
10. Write the correct number of charge on the ion or its IUPAC name.
11. Do not record wrong ion together with the correct ones in your inference.
12. Avoid the use of may be present, likely present or suspected in your inference as much
as possible.
13. Test should be performed according to the systematic steps provided in the instruction.

TEST OF KNOWN COMPOUND

ILLUSTRATION 1

A is lead(II) trioxonitrate(V) crystals.

B is zinc tetraoxosulphate(VI) crystal

Carry out the following exercises on A and B. Record all the observations and inferences clearly
in the table provided.

a. Put a spatulaful of A in a test tube and add 5cm3 of distilled water. Stir well. Test the mixture
with litmus paper.
b. Divide the solution into three portions.

i. To the first portion, add NaOH(aq) in drops and then in excess

ii. To the second solution, add NH3(aq) in drops, then, in excess

iii. To the third portions, add few drops of K2Cr2O4(aq)

c. Put all of B in a test tube and add few 5cm3 of distilled water. Stir well.

d. Divide the solution into two portions:

i. To the first portion, add NaOH(aq) in drops and then in excess

17
 ii. To the second solution, add NH3(aq) in drops, then, in excess

Test Observation Inference

bi.

ii

iii.

c.

di.

ii

ILLUSTRATION 2

C is Copper(II) tetraoxosulphate(VI). Carry out the following exercises on each sample. Record
your observation and identify any gases evolved. State the conclusion you drawn from the result
of each test.
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a. Put spatulaful of C in a beaker and add about 10cm3 of distilled water, stir well. Divide the

solution three two potions

i. To the first portion, add NaOH(aq) in drops and then in excess

ii. To the second solution, add NH3(aq) in drops, then, in excess

iii. To the third portions, add 3 drops of BaCl2(aq), followed by dilute HCl.

TEST OF UNKNOWN SAMPLES

EXPERIMENT 1

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Credit will be given for strict adherence to the instructions, for observations precisely recorded
and for accurate inferences. All tests, observations and inferences must be clearly entered in this
booklet, in ink, at the time they are made

Y and Z are different samples of inorganic simple salts. Carry out the following exercises on each of
the sample, record your observations and identify any gases evolved. State the conclusion you draw
from each test

ai. Put all of Y in a test tube and add about 5cm3 of distilled water. Stir and test the

solution with litmus paper.

ii. To the first portion, add NaOH(aq) in drops and then in excess

iii. To the second solution, add NH3(aq) in drops, then, in excess

iv. To the third portions, add 3 drops of BaCl2(aq), followed by dilute HCl.

bi. Put half of Z in a test tube and heat strongly

ii. To the remaining of Z, add about 10cm3 of distilled water, stir well. Divide the solution

into portions:

iii. To the first portion, add NaOH(aq) in drops and then in excess

iv. To the second portion, add K2Cr2O4 solution

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EXPERIMENT 2

C and D are two different inorganic samples. Carry out the following exercises on each sample.
Record your observation and identify any gases evolved. State the conclusion you drawn from the
result of each test.

a. Put spatulaful of C in a beaker and add about 10cm3 of distilled water, stir well. Divide the

solution three two potions:

i. To the first portion, add NaOH(aq) in drops and then in excess

ii. To the second solution, add NH3(aq) in drops, then, in excess

iii. To the third portions, add 3 drops of BaCl2(aq), followed by dilute HCl.

b. Put D in a test tube and add about 5cm3 of NaOH solution and heat

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EXPERIMENT 3

C and D are two different inorganic samples. Carry out the following exercises on each sample.
Record your observation and identify any gases evolved. State the conclusion you drawn from the
result of each test.

a. Put spatulaful of C in a beaker and add about 10cm3 of distilled water, stir well. Divide the

solution three two potions:

i. To the first portion, add NaOH(aq) in drops and then in excess

ii. To the second solution, add NH3(aq) in drops, then, in excess

iii. To the third portions, add 3 drops of BaCl2(aq), followed by dilute HCl.

bi. Heat a portion of D strongly in a test tube.

ii. Put the rest of D in a test tube and add about 10cm3 of distilled water. Shake the mixture

iii. Put about 2cm3 of the mixture from bii. In a test tube. Add NH3 solution in drops and then in

excess

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EXPERIMENT 4

23
P, Q and R are different organic compounds. Carry out the following exercises on each sample.
Record your observation and identify any gases evolved. State the conclusion you drawn from the
result of each test.

ai. Add about 5cm3 of distilled water to a portion of P and test the solution with litmus

paper.

ii. Add about 2cm3 of Fehling’s solution to the resulting mixture in ai. above.

b. Put about 1cm3 portions of Q in a test tube and add about 2cm3 of acidified K2Cr2O4

solution. Warm the mixture and leave to stand for about 5 minutes.

c. Add about 2cm3 of distilled water to sample R in a test tube. Add a few drops of NaOH

and swirl briefly. Then add a few drops of CuSO4 solution and swirl the mixture

Experiment 5

24
C is an organic compounds. Carry out the following exercises on sample C. Record your
observation and identify any gases evolved. State the conclusion you draw from the result of each
test.

a. Put about 10 drops of C on watch glass and ignite it using a burning splint

bi. Put about 1cm3 of C in a test tube and add about 1cm3 of distilled water. Shake the test

tube.

ii. Put about 1cm3 portions of Q in a test tube and add about 2cm3 of acidified K2Cr2O4

solution. Warm the mixture and leave to stand for about 5 minutes.

c. Put few crystals of specimen D in a test tube and add about 2cm3 of C followed by about

2cm3 of 10% NaOH solution. Shake the test tube vigorously.

d. State the class of compounds to which C belong.

Experiment 6

25
C is a mixture of inorganic compounds

Carry out the following exercises on sample C. Record your observation and identify any gases
evolved. State the conclusion you drawn from the result of each test.

Test Observation Inference

a. C + distilled water and
filter
bi. Filtrate + AgNO3
+ HNO3
Ii Resulting mixture in bi.
+ excess NH3(aq)

ci. Residue + dilute HCl

Ii Portion of mixture from

ci. + NH3(aq) in drops
then in excess

EXPERIMENT 7

X is a mixture of organic and inorganic salts.

Carry out the following exercises on sample X. Record your observation and identify any gases
evolved. State the conclusion you drawn from the result of each test.

Test Observation Inference

a. X + water, stirred and
Filtered
B Portion of filtrate from a
26
 + NaOH(aq)
In drops;
then in excess
C Portion of filtrate from a
+ NH3(aq)
In drops;
then in excess
D Portion of filtrate from a
+ KI(aq)
e. Portion of filtrate from a
+ conc. H2SO4 + heat
f. Residue from a. + iodine
solution

EXPERIMENT 8

B is a mixture of two organic salts.

Carry out the following exercises on sample C. Record your observation and identify any gases
evolved. State the conclusion you drawn from the result of each test.

Test Observation Inference

a. B + water, stirred and
filtered
Bi Filtrate from a + litmus
paper
Ii Filtrate + fehling’s
solution + heat
Ci Residue + water + heat

Ii Residue + iodine solution

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EXPERIMENT 9

G is an inorganic salt.

Carry out the following exercises on each sample G. Record your observation and identify any
gases evolved. State the conclusion you drawn from the result of each test.

Test Observation Inference

a. G + Heat

bi. G + water

Ii Solution G + litmus
paper

ci. Solution G + excess

NaOH + warm

Ii Solution G + AgNO3
+ HNO3
+ NH3

EXPERIMENT 10

28
C contains two cations and two anions.

Carry out the following exercises on sample C. Record your observation and identify any gases
evolved. State the conclusion you drawn from the result of each test.

a. Dissolve all of C in about 10cm3 of distilled water. Stir the resulting mixture thoroughly.

i. To about 2cm3 of the solution, add AgNO3 solution, followed by HNO3 solution. To the

mixture, add excess NH3 solution.

ii. To another 2cm3 portion of the solution, add dilute HCl solution followed by BaCl2 solution

iii. To another 2cm3 portion of the solution, add NaOH solution dropwise and then in excess.

Warm the mixture

iv. To another 2cm3 portion of the solution, add NH3 solution dropwise and then in excess.

EXPERIMENT 11
29
C is an organic compound. D is an inorganic compound.

Carry out the following exercises on sample C and D. Record your observation and identify any
gases evolved. State the conclusion you drawn from the result of each test.

Test Observation Inference

ai. C + distilled water and
shake
ii. Solution C + litmus
paper
iii. Solution C + Fehing’s
solution A and B + heat
bi. D + heat

Ii D + dilute HCl + heat

iii. Solution D + NaOH in

drops and then in
excess
iv. Solution D + NH3 in
drops and then in
excess

EXPERIMENT 12

F is a mixture of organic and inorganic salts.

Carry out the following exercise on sample F. Record your observation and identify any gases
evolved. State the conclusion you drawn from the result of each test.

Test Observation Inference

a. X + water and
Filtered
bi. Filtrate + litmus paper

ii. Filtrate + NaOH(aq) +

30
 warm/heat

iii. Filtrate + HNO3(aq)

+ AgNO3(aq)
c. Mixture from biii. +
excess NH3(aq)
di. Residue + water + heat

ii. Mixture from di. + iodine

solution. Mixture heated
and allowed to cool

REFERENCES

Godwin O. Ojokuku (2012) Practical Chemistry for Schools and Colleges. MacChin
Multimedia Desighners, Zaria.

Osei Yaw Ababio (2010) New School Chemistry for Senior Secondary Schools. African First
Publisher Plc, Onitsha.

Bashir A. Abba, Gabi Baba (2014) Understanding Practical Chemistry for Schools and
Colleges. Zusalat Company, G 29 Gwari Road by Cameroon Road, Doka District,
Kaduna.

A. A. Demehin etal. (2013) Macmillan Chemistry for Senior Secondary Schools. Macmillan
Nigeria Publishers Limited, Ilupeju Industrial Estate, Lagos.

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