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Winter 2013
Experiment 2
Reactions and Identification of Some Common Anions
Purpose of lab
During your previous chemistry courses, you will have come across a number of
examples of reactions of anions when the emphasis was on some other aspect of chemistry and
you may have forgotten the details of the reactions. However this course is all about the reactions themselves and you now will be expected to remember them! In this lab you will carry out
some reactions of the most common anions and learn how to use them as clues in the chemical
detective work of identifying unknowns. You should be able to work out, in many cases, what
the reactions are from your observations and the information given to you in the lab instructions.
Background
Anions are the negatively charged entities that are left over when an acid loses one or
more protons. They generally contain a non-metal atom and also may include up to four oxygen
atoms. You will also have met a couple of anions in which a metal in a very high oxidation state
is masquerading as the non-metal (e.g. chromate, CrO42-). Since anions are negatively charged
they cannot exist alone; electrical neutrality requires that they are associated in some way with
an equal number of positive charges in the form of cations. But nevertheless, particularly in
solution, anions have characteristic reactions which are the same whatever the associated
cation. These reactions, when carried out in a systematic and logical manner, enable the
anions to be identified.
Prelaboratory Preparation
Before you begin any experimental work, read the document “Important Information for
Qualitative Tests (Experiments 1 – 3)” and the introduction above. Clarify anything you do not
understand with an instructor. Observations will be recorded in the provided tables.
Ensure that your observations are initialled by an instructor before you leave C-5001 at the end
of each lab period. The hand-in sheets should contain a summary of the observations you
made for each test, including initial observations of the reagents used.
Types of reactions
There are five general types of reactions that an anion may undergo:
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Winter 2013
Types of reactions (continued)
P1.
Protonation.
If the anion is derived from a weak acid, the addition of strong acid will protonate the
anion. Some of the acids so formed are volatile and can be determined by smell (e.g. acidified
acetates smell of vinegar). More usefully for identification purposes, several of the weak acids
are unstable themselves and decompose to give a gas and water.
For example for nitrite:
2 NO2- (aq) + 2 H+ (aq) → [2 HNO2 (aq)] → NO (g) + NO2 (g) + H2O (l)
This example was chosen because it is the most complicated; usually only one gas is
produced. (As we shall see later, nitrogen is a bit peculiar in its choice of oxidation states for
stable oxides.) The gas produced can be identified by its colour, smell or chemical reactions.
P2.
Thermal decomposition. When a solid containing the anion is heated, it may decompose to give a volatile oxide of the non-metal present in the anion and a residue of the
metal oxide:
e.g.
CaCO3 (s) → CaO (s) + CO2 (g)
When a lower oxidation state of the non-metal exists, it may just lose oxygen, leaving an
anion containing the non-metal in the lower oxidation state: e.g.
2 NaNO3 (s) → 2 NaNO2 (s) + O2 (g)
2 KClO3 (s) → 2 KCl (s) + 3 O2 (g)
Once again gas identification is involved.
P3.
Reduction. Some anions are oxidizing agents and therefore are reduced when an
oxidation–reduction (redox) reaction occurs. The iodide ion is very easily oxidized to
elemental iodine and is used to test for oxidizing agents:
2 I- (aq) → I2 (s) + 2 eThe iodine formed usually reacts with excess iodide ion to form the soluble triiodide ion,
I3-, which is easily detected by its brown colour in aqueous solution and the navy blue or
black colour it produces with starch.
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Winter 2013
Types of reactions (continued)
P4.
Oxidation.
Other anions are reducing agents that can be oxidized to an anion of the
non-metal in a higher oxidation state (e.g. sulfite to sulfate)
+
SO32- (aq) + H2O (l) → SO42- (aq) + 2 H (aq) + 2 eor, in the case of the halide ions, to the halogen itself.
-
2 Cl (aq) → Cl2 (g) + 2 e-
Eº = 1.3583 V
Potassium permanganate is used to accomplish these oxidations since its intense purple
colour acts as an indicator and it is a powerful oxidant (oxidizing agent) - powerful
enough to oxidize all of the halide ions except fluoride to the elemental halogen. The
half cell reaction of the permanganate ion is:
MnO4- (aq) + 8 H+ (aq) + 5 e- → Mn2+ (aq) + 4 H2O (l)
P5.
Eº = 1.491 V
Precipitation. Most anions form insoluble precipitates with one or more cations, with
nitrate and acetate being the only common exceptions. The two most useful cations for
+
2+
anion identification are the silver ion, Ag (aq), and the barium ion, Ba (aq). They form precipitates with the anions that do not react in the first three tests, as well as some that do.
a.
Ag+ forms insoluble precipitates with the halide ions Cl- , Br- and I- . They can be
distinguished by colour and ease of dissolution in ammonia solution. There are two
competing equilibria:
Ag+ (aq) + X- (aq) ↔ AgX (s)
Ag+ (aq) + 2 NH3 (aq) ↔ [Ag(NH3)2]+
(X- = Cl- , Br- and I-)
(a complex ion)
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Winter 2013
Types of reactions (continued)
P5.
a.
Precipitation.
+
Formation of the complex ion removes Ag from the solution so the precipitate
redissolves to replace it - the ion product may no longer exceed the solubility product
constant. Look at the following table to decide the order of ease of solubility.
Solubility products of silver halides
Ksp (AgCl) = 2.0 x 10-10 mol2.L-2
Ksp (AgBr) = 5.0 x 10-13 mol2.L-2
Ksp (AgI) = 8.0 x 10-17 mol2.L-2
In neutral solution, Ag+ also forms precipitates with some ions of weak acids which will
have been detected above. These differ from the halides in that the precipitates are
soluble in strong acid, reacting as in test P1.. (The hydrohalic acids - HCl, HBr and HI are all strong acids.)
b.
2+
Ba forms insoluble precipitates with most ions that have two or more negative
charges. If the acid from which the anion is derived is a weak acid, then the precipitate
will dissolve in strong acid (see P1. above). If the acid does not decompose, then we again
have two competing equilibria and a similar situation to that with silver ion and ammonia –
except that this time it is the anion's concentration that is affected:
3 Ba2+ (aq) + 2 PO43- (aq) ↔ Ba3(PO4)2 (s)
PO43- (aq) + 3 H+ (aq) ↔ H3PO4 (aq)
Protonation of the anion removes it from solution and the precipitate dissolves to replace it.
Confirmation
The above series of tests should give you a pretty good idea of which anion is present,
or at least narrow it down to one or two. However, not all the reactions are unambiguous and it
is possible to make mistakes. Therefore, you should double check your results with a "confirmatory" test. This test, taken in conjunction with the other five tests, should lead you to a definite
conclusion when trying to identify an unknown. Simple confirmatory tests are available for most,
but not quite all, anions.
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Winter 2013
Experimental for Preliminary Tests
You should use small test tubes for all your reactions. Even though these are considered disposable, they should be rinsed and reused when possible. It is wasteful to do
otherwise. Always clean out these test tubes once you have made and recorded your observations. Use a little soapy tap water and then rinse with small amount of deionized water. The
longer they are allowed to stay dirty, the more difficult they are to clean. If you know what the
solid or precipitate is, you are more likely to know whether a drop of acid or base will help you to
remove it. You may use large test tubes to hold reagent solutions required for multiple tests.
You could lose subjective evaluation marks if you are unnecessarily wasteful with small test
tubes or solutions and if you leave test tubes behind on your bench or in a fume hood when you
leave the lab.
Notes on the identification of gases
To be prepared to test a gas, you need to think ahead. Before you mix reagents or start
heating a tube, think about which gas(es) might be evolved; the gas isn't going to wait around
while you go to look for the lime water or a splint! Collect the item(s) required to test for the
gas(es) you think may be produced (e.g. splint, 1 mL of the appropriate test solution, Pasteur
pipette etc.).
When using a Pasteur pipette to transfer a gas, squeeze the bulb before putting it
into the test tube to expel air from the pipette. Then with the tip of the pipette just above the
surface of the liquid, release the bulb gently to draw some of the gas into the pipette. Bubble
the gas slowly though the test solution to give it a chance to dissolve or react.
Remember, the gas can only contain elements that were in the original reactants
or possibly the water. Therefore, there is no need to do the lime water test if you are heating
a nitrate! In fact there is no common anion that will give oxygen, hydrogen or nitrogen from
aqueous solution in these tests, although some will give oxygen on heating the dry solid. The
only reactions that give hydrogen in aqueous conditions involve powerful reducing agents, such
as an active metal (e.g. Zn) dissolving in acid or an ionic hydride (e.g. CaH 2) reacting with water.
A summary of the tests for gases is given below.
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Winter 2013
Identification of Gases
carbon dioxide, CO2
A colourless acidic gas that turns limewater milky white.
hydrogen, H2
A colourless gas that causes a flaming splint to "pop".
oxygen, O2
A colourless gas that relights a glowing splint.
nitrogen, N2
A colourless inert gas --- no reactions.
(All the above are odourless.)
ammonia, NH3
A colourless, basic gas.
nitrogen dioxide, NO2
A brown acidic gas that dissolves in water to produce a colourless solution. It will turn moist starch-
Toxic gas: test for it in a
iodide paper navy blue or black when it comes in
fume hood!!!
contact with it.
A colourless acidic gas that dissolves in water to
sulfur dioxide, SO2
produce a colourless solution. It will turn filter paper
Toxic gas: test for it in a
moistened with acidified potassium dichromate
fume hood!!!
green when it comes in contact with it.
(These three have distinctive smells. Waft these gases to your nose if you are required
to smell them. Otherwise --- DON'T smell them!!!)
Procedure
The Preliminary Tests
The numbers of the following tests correspond to those in the introduction. Your laboratory instructor may suggest you do the tests in a particular order. If not, you may do them in any
order that suits you. When possible, test sodium salts of the anions. Not all tests will produce
positive results!!!!
P1.
Test solids containing:
i) CO3
2-
ii) CH3COO
-
iii) NO2
-
-
2-
iv) SO3
2-
2-
and v) SO4 ions.
NOTE: Test the salts containing NO2 and SO3 in a FUME HOOD!!!
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Winter 2013
The Preliminary Tests (continued)
Add 2 mL of 3 mol.L-1 sulfuric acid to a small amount of solid containing the anion to be
tested in a large test tube. Note if any gas is evolved on mixing. If a gas is formed, note
its colour and, only if the gas is colourless, note any smell. Carry out any further tests
as appropriate (see the tables in “Identification of Gases” above). If there is no gas evolution at room temperature, warm the tube carefully in a beaker of hot water until it is just
too hot to touch (about 70º C) and smell cautiously. Repeat this procedure for each
anion to be tested.
P2.
Test solids containing:
i) SO32- and ii) I- ions. Also test: iii) copper(II) nitrate
iv) sodium nitrate.
Carry out these tests in a fume hood.
Place enough solid in a dry, small, hard glass test tube to just fill the rounded bottom of
the tube. Using a test tube holder with the tube held at an angle of about 45º, heat the
bottom of the tube in a blue Bunsen flame. Heat cautiously at first in the top of the flame
and then if nothing happens, lower the test tube slowly to the hottest part of the flame,
just above the blue cone. Do not point the test tube at yourself or anyone else!
Once again, observe and test any gases that are evolved. Once they have cooled, dispose of these test tubes in the glass garbage. Do not place hot test tubes in a plastic
or wooden rack but rather in a beaker!!!
Note 1:
Some ionic compounds may decompose without much sign of anything happening.
You should test for the likely gases that could form anyway.
Note 2:
Some salts will melt before decomposing to give a gas; continue to heat strongly
after the solid melts.
Note 3:
This test is influenced by the cation. In general the smaller the cation, the easier it
is to decompose the anion. In the case of some carbonates (e.g. K+, Na+, Ca2+),
the Bunsen flame may not be hot enough to cause significant decomposition (but they all react
with strong acid).
For tests P3. and P4., make and use an acidified solution of the anion by adding
1 mL of 3 mol.L-1 sulfuric acid to 2 mL of a 5% solution. If you are uncertain if the solution is acidic, test with full range pH paper and then add more acid drop wise, if necessary.
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Winter 2013
The Preliminary Tests (continued)
P3.
Test solutions containing:
-
i)
CH3COO
-
ii) NO2
iii) NO3
-
2-
-
iv) SO4 and v) Cl ions.
Place one drop of the acidified solution onto a piece of starch-iodide paper. A navy blue
or black colour indicates the release of elemental iodine (strictly this is a test for the I3ion).
P4.
Test solutions containing:
i)
NO2
-
ii) NO3
-
2-
iii) SO3
-
-
iv) Cl and v) Br ions.
Add 5 drops of potassium permanganate solution to the remaining portion of the acidified solution. Note whether or not the colour of the permanganate solution remains. If
you do not get an immediate reaction, warm the solution in a warm water bath.
Compare your results to those observed when KMnO4 (aq) is added to water.
Note:
If you have forgotten to add acid or not added enough, a brown precipitate of MnO2 may
form. You may be able to recover by adding acid afterwards but if the brown precipitate
remains, start again.
P5. a.
Test solutions containing:
i)
CO32-
ii) CH3COO-
iii) Cl- and iv) I- ions.
To 2 mL of a neutral dilute solution of your anion, add silver nitrate solution dropwise. If
a precipitate forms, add about 1 mL of silver nitrate in total. Note the colour of the precipitate.
Use roughly 10 drops of the precipitate mixture produced above to perform each
of the tests below.
i.
Add 6 mol.L-1 aqueous ammonia to 10 drops of precipitate mixture until either the
precipitate redissolves or the volume is increased by about 50%.
ii.
Add 6 mol.L-1 nitric acid to 10 drops of precipitate mixture until the precipitate
redissolves or the volume is increased by about 50%.
NOTE:
Discard any silver solutions or precipitates in the silver collection container.
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Winter 2013
The Preliminary Tests (continued)
P5. b.
Test solutions containing:
i) NO3-
ii) SO32- and iii) SO42- ions.
To 2 mL of a neutral dilute solution of your anion, add about 1 mL of 1 mol.L-1 barium
chloride (or nitrate) solution. If a precipitate forms, test its solubility in 6 mol.L-1 nitric
acid. Do this by transferring ~10 drops of precipitate mixture to another test tube. Take
this test tube to a fume hood and then add 20 drops of 6 mol.L-1 nitric acid.
NOTE:
Discard any barium solutions or precipitates in the barium collection container.
Confirmatory Tests
Rationale
Although the five "preliminary" tests may give a strong indication of which ion is
present, it is not necessarily conclusive. You also have to realize that the list of anions only
contains the most common ones and you have only been looking at one ion at a time. For example, at least two other ions will give carbon dioxide when treated with acid - hydrogen carbonate, HCO3- and cyanate ion, CNO-. (Only the alkali metals form solid hydrogen carbonates.)
Mixtures of anions would obviously give confusing results.
Ideally we would like a unique, distinctive reaction for each ion that would give unambiguous confirmation, but unfortunately such tests do not exist for all of the anions and some are
too complex or even dangerous to carry out in our circumstances. However, here are some
useful ones.
Experimental for Confirmatory Tests
Familiarize yourself with the following confirmatory tests.
Carbonate.
No useful confirmatory test. None of the other ions in this set produce
carbon dioxide when acid is added to them.
C1 Acetate.
Place a small amount of solid sodium acetate in a dry test tube and add 5 drops of concentrated sulfuric acid and 2 drops of 1-pentanol. Warm in a hot water bath for 3–4
minutes and smell carefully. Cool, add 1 mL of cold water and then pour into a watch
glass and smell. (Test P1 should have given a vinegar smell; you are now expecting a
different smell.)
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Winter 2013
Confirmatory Tests (continued)
C2 Nitrite.
(use 5% sodium nitrite)
This is the only ion in the group that is both oxidizing and reducing. Place a few crystals
of iron(II) ammonium sulfate (ferrous ammonium sulfate) into a test tube and dissolve
them in 10 drops of 3 mol .L-1 sulfuric acid. Carefully add about 1 mL of sodium nitrite
solution so that the solutions do not mix - run the solution down the side of an angled
test tube. Observe the junction of the two layers. The coloured compound is
[Fe(NO)(H2O)5]2+.
C3 Nitrate.
(Nitrate will not give a positive test under these conditions.)
(use 5% sodium nitrate)
Dissolve a few crystals of the iron(II) salt (see above) in about 1 mL of sodium nitrate
and then run 10 drops of concentrated sulfuric acid (kept in a fume hood) down the side
of the angled tube so that it forms a separate layer underneath. Again observe the junction of the two layers. The colour is due to the same compound as in the nitrite test, but
nitrate requires much stronger acid.
(Obviously this one works for nitrite too so you
must be sure that is not present.)
C4 Sulfite.
(use 5% sodium sulfite) This test MUST be done in a fume hood.
The smell of SO2 and its reducing properties are distinctive. Repeat test P1. from the
preliminary tests and test the vapours formed over the hot solution with a small strip of
filter paper moistened with acidified potassium dichromate solution. Observe and note
any colour change.
(Note:
SO2 rarely comes bubbling out of aqueous solutions like
CO2; it is too soluble. However, the vapours over a hot solution contain enough SO 2 to
smell and react.)
Sulfate.
There is really nothing else that is useful; sulfate ion just isn't very reactive.
NOTE: The following three tests should be carried out in a fume hood.
C5a Chloride. (use sodium chloride)
Mix a little of the solid with an equal amount of manganese(IV) oxide (manganese dioxide) in the bottom of a dry test tube. In a fume hood add 5 drops of concentrated sulfuric
acid and then warm the test tube. Observe the colour of the liberated gas and test it with
moist blue litmus and starch-iodide papers.
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Winter 2013
Confirmatory Tests (continued)
C5b Bromide.
(use potassium bromide)
Same test as for chloride. Collect a little of the gas in a pipette and dissolve in 1 mL of
water. Note the colour of the solution and compare it with NO2.
C5c Iodide.
(use potassium iodide)
This time MnO2 isn't necessary, just add the sulfuric acid. The colour of the vapour is
quite unique.
49
Lab slot _______
Partner:
Bench # _______
Bench # _______
Winter 2013
Name ____________________________________
Name ____________________________________
Observations for Test P1.
3 mol / L H2SO4 (aq):
Anion
Test P1.
Acidification
CO32- (*)
CH3COO- (*)
NO2- (*)
(*)
Indicate the actual solid used (e.g. Na2CO3) and note its appearance (e.g. white powder)
50
Lab slot _______
Bench # _______
Winter 2013
Name ____________________________________
Observations for Test P1.
Anion
Test P1.
Acidification
SO32- (*)
SO42- (*)
(*)
NO3-, Cl-, Br-
No gas formed and therefore no reaction.
I-
No reaction expected but may turn yellow due to dissolved O2.
Indicate the actual solid used (e.g. Na2CO3) and note its appearance (e.g. white powder)
51
Lab slot _______
Bench # _______
Winter 2013
Name ____________________________________
Observations for Test P2.
Anion
CO32-
Test P2.
Thermal Decomposition
The white solid melts upon heating to produce a colourless liquid.
When this liquid is heated, a colourless, odourless gas produced which
turns moist blue litmus paper red. The gas produces a milky white precipitate when bubbled into lime water. (Difficult with some cations)
CH3COO-
Chars and smells of vinegar.
NO2-
The white solid melts upon heating to produce a colourless liquid.
When this liquid is heated, variable results can occur depending on the
cation. May give colourless gas which relights a glowing splint and / or
a brown gas.
NO3- (*)
(*)
SO42-
No reaction generally. Depends on the cation present.
Cl-
No observed change and therefore no reaction.
Br-
No observed change and therefore no reaction.
Indicate the actual solid used (e.g. Na2CO3) and note its appearance (e.g. white powder).
52
Lab slot _______
Bench # _______
Winter 2013
Name ____________________________________
Observations for Test P2.
Anion
Test P2.
Thermal Decomposition
SO32- (*)
I- (*)
(*)
Indicate the actual solid used (e.g. Na2CO3) and note its appearance (e.g. white powder).
53
Lab slot _______
Bench # _______
Winter 2013
Name ____________________________________
Observations for Tests P3.
Starch-iodide paper:
Test P3.
For Oxidizing Properties
Anion
CO32-, SO32-, Br-, I-
Starch-iodide paper gets wet but does not change colour.
No reaction.
CH3COO- (*)
NO2- (*)
NO3- (*)
SO42- (*)
Cl- (*)
(*)
Indicate the appearance of the solution containing the anion
(e.g. a clear, colourless solution)
54
Lab slot _______
Bench # _______
Winter 2013
Name ____________________________________
Observations for Test P4.
KMnO4 (aq):
Test P4.
For Reducing Properties
Anion
CO32-, CH3COO-,
SO42-
Mixture is a purple colour. No reaction.
NO2- (*)
NO3- (*)
SO32- (*)
Cl- (*)
Br- (*)
Permanganate decolourized. A yellow or orange or brown solution
with a black precipitate results.
I-
(*)
Indicate the appearance of the solution containing the anion
(e.g. a clear, colourless solution)
55
Lab slot _______
Bench # _______
Winter 2013
Name ____________________________________
Observations for Test P5a.
AgNO3 (aq):
6 mol / L NH3 (aq):
6 mol / L HNO3 (aq):
Test P5a.
Silver ion
Anion
CO32- (*)
CH3COO- (*)
NO2-
A white precipitate forms that dissolves in dilute nitric acid.
Brown gas is produced as in test P1..
NO3-
No observed change. No precipitate.
SO32(*)
White precipitate.
(Complex reaction - not a reliable test.)
Indicate the appearance of the solution containing the anion
(e.g. a clear, colourless solution)
56
Lab slot _______
Bench # _______
Winter 2013
Name ____________________________________
Observations for Test P5a.
Anion
Test P5a.
Silver ion
SO42-
No observed change.
No precipitate unless solution is very concentrated.
Cl- (*)
Br-
Very pale yellow precipitate forms that darkens in light.
The solid is slightly soluble in ammonia but not in nitric acid.
I- (*)
(*)
Indicate the appearance of the solution containing the anion
(e.g. a clear, colourless solution)
57
Lab slot _______
Bench # _______
Winter 2013
Name ____________________________________
Observations for Test P5b.
BaCl2 (aq):
6 mol / L HNO3 (aq):
Anion
Test P5b.
Barium ion
CO32-
A white precipitate forms. This precipitate dissolves in
HNO3 (aq), giving gas as in test P1.
CH3COO-
No precipitate is observed but a clear, colourless solution results.
NO2-
No precipitate is observed but a clear, colourless solution forms.
NO3- (*)
SO32- (*)
SO42- (*)
Cl-, Br-, I-
(*)
No precipitate is observed but a clear, colourless solution results.
Indicate the appearance of the solution containing the anion
(e.g. a clear, colourless solution)
58
Lab slot _______
Bench # _______
Winter 2013
Name ____________________________________
Observations for the Confirmatory Tests
concentrated H2SO4 (aq):
iron(II) ammonium sulfate:
3 mol / L H2SO4 (aq):
Anion (*)
Confirmatory tests
1-pentanol:
CH3COO-
NO2-
NO3-
(*)
Identify the compound used and indicate its state
(s or aq).
59
Lab slot _______
Bench # _______
Winter 2013
Name ____________________________________
Observations for the Confirmatory Tests
concentrated H2SO4 (aq):
3 mol / L H2SO4 (aq):
manganese(IV) oxide:
Anion (*)
SO32-
Confirmatory tests
acidified K2Cr2O7:
Cl-
Br-
I-
(*)
Identify the compound used and indicate its state
(i.e. solid).
60
Lab slot _______
Partner:
Bench # _______
Bench # _______
Name ____________________________________
Name ____________________________________
Preliminary Tests:
NOTE:
1.
Winter 2013
Conclusions
Include references for all reaction equations below.
Write the equations for the reaction that occurs when aqueous sulfuric acid is added to an aqueous solution of nitrite ion.
2.
Write a balanced equation for the reaction between carbon dioxide and limewater
(saturated calcium hydroxide solution)
3.
Write the equation for the reaction that occurs when aqueous sulfuric acid is added
to an aqueous solution of carbonate ion.
4.
What is the: a) colourless gas b) brown gas that can form when a nitrate salt
is thermally decomposed? Write the balanced reaction equations showing gas or
gases being produced from i) sodium nitrate
a)
i)
ii)
b)
ii) lead(II) nitrate.
61
Lab slot _______
Partner:
Bench # _______
Bench # _______
Name ____________________________________
Name ____________________________________
Preliminary Tests:
5.
Winter 2013
Conclusions
Write the equation for the reaction that occurs when calcium carbonate is thermally
decomposed.
6.
Write the equation for the reaction that occurs when concentrated sulfuric acid is
added to an iodide salt and the resulting mixture is heated.
7.
Show, using the appropriate half-reactions, how you obtain the chemical equation
for the reaction that occurs when aqueous potassium permanganate is added to
an aqueous solution of bromide ion under acidic conditions.
8.
Write a balanced chemical equation for the reaction that occurs when the precipitate formed from the reaction of silver ion with chloride ion dissolves in aqueous
ammonia.
62
Lab slot _______
Partner:
Bench # _______
Bench # _______
Name ____________________________________
Name ____________________________________
Confirmatory Tests:
9.
Winter 2013
Results and Conclusions
Write a balanced equation for the reaction that occurs when the precipitate
formed from the reaction of barium ion with carbonate ion dissolves in nitric acid.
C4 Sulfite.
What is the final colour of the filter paper? __________________________________
The dichromate has been converted to Cr3+ (aq). What is this "conversion" process
called? ________________________________
Write a balanced chemical reaction for the conversion process referred to above.
C5 Halides.
What is the colour of the gas or vapour and the formula of the
substance responsible for it in each case below?
Chloride
Colour
Chemical
Formula
Bromide
Iodide
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Lab slot _______
Bench # _______
Name ____________________________________
Confirmatory Tests:
C5 Halides.
Winter 2013
Results and Conclusions
For tests on the chloride ion:
Write a balanced chemical reaction showing the gas produced when chloride ion reacts
in this confirmatory test.
Describe what happened to the blue litmus paper:
Describe and explain what happened to the starch-iodide paper:
What is the "conversion" process that takes place for a component of the
starch-iodide paper during a positive test?
References
R.H. Petrucci, W.S. Harwood and F.G. Herring. General Chemistry, any edition.
P. Atkins et al., Shriver & Atkins Inorganic Chemistry, fourth edition.
G. Svehla. Vogel's Qualitative Inorganic Analysis, sixth edition.