OUR LADY OF THE ROSARY COLLEGE
CHEMISTRY PRACTICAL MANUAL
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Advanced Level
Experiment should be carried out under the supervision of a Chemistry teacher
Safety precaution must be noted.
Division of work: Individual/ Two-students group
Pre-laboratory work
Read the experimental steps carefully and try to list all safety precautions.
Qualitive analysis of inorganic salts by means of non-systemic method
Additional Apparatus: Platinum wire for flame test and cobalt glass.
Chemicals: They are bench solutions and obtainable on the side bench.
NOTE: Amount of sample is limited. You must handle your sample carefully and record the sample
number. No more sample will be supplied in normal case.
Guideline:
The following notes serve guidelines to the relation between certain observations and the
chemical nature of a limited number of compounds. Through the observations of some tests on
inorganic salts, most of them can be recognized. However, these notes are not exhaustive and indeed
the information is necessarily restricted but, from your knowledge of the periodic table and general
chemistry, you should be able to make sensible extrapolations to other compounds not included here.
Test
1. Colour
Most inorganic salt are colourless or white solids. Colourlful salts are also numerous but the
colours of ions give you valuable information. For example,
Copper(II)
Blue to green
Iron(II)
green
Iron(III)
Yellow to brown
Cobalt(II)
pink
Nickel(II)
green
Chromium(III)
green
Chromate(VI)
yellow
Dichromate(VI)
orange
Manganese(II)
pink
Permanganate
purple
Look up colours of most common inorganic salts.
2.
Solubility in water
Solubilities can be described roughly as: 'very soluble', 'soluble', 'slightly soluble' and 'insoluble'.
Add a small spatula of sample into water of about 3 cm high in a test tube. Observe. If it is insoluble
in water stopper it and shake it vigorously.
Water soluble substances.
(a) Cations: Salts of sodium, potassium and ammonium ion, nitrate(V) and nitrate(III), (silver (I)
nitrate(III) sparingly soluble).
(b) Anions: Chlorides, bromides, iodides, chlorates(V) and bromate(V) (except those of silver(I),
mercury(I) and copper(I).). Lead halides and barium bromate(V) are sparingly soluble in cold
water. Sulphates(VI), except those of barium, strontium and lead (calcium, mercury(II) and silver(I)
sulphates(VI) are very sparingly soluble.). Manganates(VII) (permanganate), chlorates(I)
ethanoates, and methanoates. (Silver(I) and mercury(I) ethanoates and methanoates and lead(II)
methanoate are sparingly soluble.)
3. Action of heat : Heat 1 - 2 small spatula of sample in a combustion tube.(which is smaller than
what you commonly use.) by using a non-luminous Bunsen flame. Observe the change of the solid and
any gas evolved. Describe the appearance of the gas and test the gas.
Expected results:
(a) Ammonium salts, mercury(II) halides and sulphide, arsenic(III) and antimony(III) oxides,
sulphur and iodine sublimes.
(b) Nitrates(III) nitrates(V) except those of potassium, sodium and ammonium give brown fumes of
nitrogen dioxide.
(c) Many carbonates, all hydrogen carbonates, ethanoates (these also give carbon monoxide).
(d) Sulphate(IV) (except those of sodium and potassium), thiosulphates(VI) and some sulphates(VI)
give sulphur dioxide. Some sulphides give hydrogen sulphide through hydrolysis.
(e) Many ammonium salts and amines give ammonia.
(f) Methanoates give hydrogen (and other gases), organic compounds may give inflammable
vapours having smells e.g. propanone from ethanoates, methanal from methanoates.
4. Flame test
In this experiment, a platinum wire with glass handle is cleaned by the following steps.
(i) Immerse the wire into conc. nitric acid;
(ii) Burn the wire in a colourless Bunsen flame until there is no colour.
The wire is then ready to be used. If a sample solution is being tested, immerse the wire into the
solution and then put the wire into a colourless flame and note the colour of the flame. Caution should
be made not to burn the glass part of the platinum wire; otherwise, it will be broken.
Sodium compounds give a golden yellow colour. Potassium compounds give a lilac colour
appearing crimson when viewed through a considerable thickness of cobalt glass. Calcium compounds
give a yellowish red colour. Strontium and lithium compounds give a crimson colour. Barium
compounds give a yellowish green colour. Lead, arsenic, antimony and bismuth compounds give a
greyish blue colour (and attack the platinum).
5. Action of dilute hydrochloric and sulphuric(VI) acids
Insoluble chlorides or sulphates(VI) may precipitate with the appropriate acid, Carbonates and
hydrogen carbonates give carbon dioxide. Nitrates(III) give brown fumes of nitrogen dioxide.
Sulphates(IV) and thiosulphate(VI) give sulphur(IV) dioxide. (Thiosulphate(VI) also give a precipitate
of sulphur). Sulphides give hydrogen sulphide. Chlorates(I) give chlorine.
6. Action of concentrated sulphuric(VI) acid
In addition to the reactions occurring with dilute sulphuric(VI) acid,
(i) Halides give the corresponding hydrogen halide or even halogen.
(ii) Sulphates(IV) give sulphur(IV) dioxide.
(iii) Methanoates give carbon monoxide (even at room temperature), ethanedioates give carbon
monoxide and dioxide and ethanoates give a smell of vinegar.
(iv) Certain reducing agents such as iron, copper, iodides, bromides give sulphur(IV) dioxide.
7. Action of concentrated nitric(V) acid
Reducing agents reduce the reagent to brown nitrogen dioxide. Many metal nitrates are soluble.
characteristic colour of transition metals should be noted. Some metal compounds, when reacted with
the acid, give higher oxides of metals such as tin and antimony; these higher oxides are formed as
precipitates. Iron(II) compounds cause the liquid to go back.
8. Action of sodium hydroxide solution
Sulphides of arsenic, antimony and tin dissolve (even though insoluble in water). Metallic
hydroxides are precipitated and, if amphoteric, redissolve in excess of the reagent. Ammonium salts
give ammonia on heating.
9. Action of ammonia solution
Silver(I) chloride and arsenic(III) sulphide dissolve. Metallic hydroxides are precipitated, those of
some transition metals dissolve in excess of the reagent giving colourful amines.
10. Action of acidified manganate(VII)
Reducing agents such as iron(II), mercury(I) and tin(II) salts, sulphates(IV) (sulphites), sulphides,
methanoates and ethanedioates reduce manganate(VII) to hydrated manganese(IV) oxides or to
manganese(II) at room temperature or on heating.
11. Action of hydrogen sulphide solution
Solutions of some cations give precipitates of sulphides (often highly coloured). Those of lead(II),
silver(I), mercury(II), copper(II), iron(II), cobalt(II) and nickel(II) are back, bismuth(III) and tin(II) are
brown, cadmium(II), tin(IV), and arsenic(III) and (V) are yellow, antimony(III) and (V) are orange,
zinc(II) is white and manganese(II) is pale pink. Many oxidizing agents, e.g.; iron(III) are reduced
with production of colloidal sulphur.
12. Properties and tests for gases
(a) Hydrogen: Colourless, odourless, burns with a pale blue flame and slight explosion.
(b) Carbon dioxide: Colourless, odourless, turns lime water milky.
(c) Sulphur(IV) dioxide: Colourless, distinctive smell, turns dichromate(VI) impregnated filter paper
green.
(d) Hydrogen sulphide: Colourless, characteristic smell, turns lead(II) ethanoate impregnated paper
back.
(e) Chlorine: Yellowish green, characteristic smell, bleaches moist litmus paper.
(f) Oxygen: Colourless, odourless, relights a glowing splint.
(g) Nitrogen dioxide: Brown gas, distinctive smell. Turns starch-iodide paper blue.
(h) Bromine: Reddish brown vapour, characteristic smell. Turns fluorescein impregnated paper red.
(i) Iodine: Purple vapour characteristic smell. Turns starch impregnated paper blue.
(j) Ammonia: Colourless, characteristic smell. Turns red litmus blue.
(k) Carbon monoxide: Colourless, odourless, burns with a pale blue flame.
(l) Hydrogen chloride and bromide: Colourless, characteristic smell.Give white fumes with
ammonia.
Caution: General safety precaution must be noted. Attention must be paid to the use of concentrated
acids, alkalis and redox reagents.
How to access your report?
Observations: 60% of the marks; interpretation: 40% of the marks
You should give your reasons clearly and show that how can you get your conclusion (that is, the name
of the unknown sample).
OUR LADY OF THE ROSARY COLLEGE
Qualitative Analysis RESULT SHEET
Date: _____________ Name:__________(
) Class:___ No.___ SAMPLE NUMBER : ___
1. Appearance: colour ______________________, state ___________________
TEST
OBSERVATIONS
2 Try to dissolve the sample in water
(a) Solubility
(b) Is any gas evolved? (Test the gas)
3 Approximate pH value of the aqueous
solution or suspension using pH paper
4 Action of heat (Use a combustion tube)
Is any gas evolved? (Test the gas)
5 Flame test
6 Action of 2 M HCl on the solid or its
aqueous solution
7 Action of 1 M H2SO4 on the solid or its
aqueous solution.
8 Action of concentrated H2SO4 on the
solid; warm the mixture if there is no
reaction.
9 Action of concentrated HNO3 on the
solid
10 Action of 2 M NaOH (solid or its
aqueous solution)
Several drops:
In excess:
11 Action of 2 M ammonia (solid or its
aqueous solution)
Several drops:
In excess:
12 Action of acidified KMnO4 solution on
the solid or its aqueous solution
13 Action of an aqueous H2S solution on a
solution or suspension of the sample in
water
14 Action of aqueous sodium sulphate(IV)
solution.
15 Other tests [You must ask for the permission from your teacher.]
Hand in your report to Mr. Lam before 4:30 p.m.
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