Welding Australian practices codes and specs.ppt

Detailed welding methods and welder instructions of all grades

2. Objective
To identify the contents of thirteen different test tubes
using a few simple tests and their mutual reactivities.
Color – Transition metals tend to form brightly colored
compounds.
Odor – Some compounds have very distinctive odors.
When testing for odor always remember to WAFT!
pH – Using universal litmus paper determine the pH of
the compound.
Solubility – By combining the unknowns and knowing the
rules of solubility, one can determine the contents
of the test tubes.
Flame Test – Metal ions when introduced into a flame
give a distinct emission spectrum. The color of the
flame can help identify the unknown metal.
Simple Tests

3. Definitions Applicable to Ionic Reactions
Ions – Charged Species. Metals tend to form cations
and Nonmetals tend to form anions.
Ionic substances tend to dissolve readily in water to
form solutions because they are charged
particles that should electrostatically attract
the corresponding end of the water dipole.
However, not all ionic substances are soluble in water,
indicating that they do not have enough energy
to break apart the ionic crystal.
Cations – Positively charged ions. Cations in today’s
experiment include: H
+
, Na
+
, K
+
, Ca
2+
, Ba
2+
,
Fe
3+
, Cu
2+
, Ni
2+
, and Sn
2+
.
Anions – Negatively charged ions. Anions in today’s
experiment include: Cl
-
, S
2-
, NO
3
-
, SCN
-
, SO
4
2-
,
CrO
4
2-
, and C
20
4
2-
.

4. Soluble - The term soluble means that a substance dissolves. 
An aqueous solution is soluble.  If one mixes two solutions
together and no precipitate forms, then only the ions are
in solution.  Thus, there is no reaction.
Note: Sometimes two solutions are mixed together, a reaction
can occur that does not form a precipitate.  Usually when
this type of reaction takes place, there is a marked
color change when the product is formed or a large
temperature change is observed.
Insoluble - The term insoluble means a
substance does not dissolve. 
Precipitate – A solid beneath a liquid.  If one
mixes two solutions and a solid forms,
this is called a precipitation reaction.

5. Solubility Rules
1. All nitrates, chlorates, and acetates of all metals are
soluble. Silver acetate is sparingly soluble.
2. All sodium, potassium, and ammonium salts are soluble.
3. All chlorides, bromides, and iodides are soluble except silver,
lead (II), and mercury (I).
4. All sulfates are soluble except barium, calcium, strontium,
lead (II), and mercury (I).
5. Carbonates, phosphates, borates, sulfites, chromates, and
arsenates of sodium, potassium, and ammonium are
soluble; all others are insoluble.
6. Sulfides of barium, calcium, magnesium, sodium, potassium,
and ammonium are soluble; all others are insoluble.
7. Hydroxides of sodium, potassium, and ammonium are soluble.
Hydroxides of barium and calcium are moderately soluble.
8. Everything else will be considered insoluble!

6. Overall Equation – Shows reactants and products
as undissociated, electrically neutral compounds.
Complete Ionic Equation – Shows the state of
reactants and products as hydrated or other
phases.
Ag
+1
(aq) + NO
3
-1
(aq) + Na
+1
(aq) + Cl
-1
(aq) Na
+1
(aq) + NO
3
-1
(aq) + AgCl
(s)
AgNO
3(aq)
+ NaCl
(aq)
NaNO
3(aq)
+ AgCl
(s)

Ionic Equations & Precipitation Reactions
Net Ionic Equation – Shows only the reactants
and products that are directly involved in the
reaction.
Ag
+1
(aq) + Cl
-1
(aq) AgCl
(s)

7. Spectator Ions – Ions which are not directly
involved in the net ionic equation are called
spectator ions. In the previous equation, this
would be the sodium and nitrate ions.
Ag
+1
(aq) + NO
3
-1
(aq) + Na
+1
(aq) + Cl
-1
(aq) Na
+1
(aq) + NO
3
-1
(aq) + AgCl
(s)
Ag
+1
(aq) + Cl
-1
(aq) AgCl
(s)
(Net Ionic Equation)
Ag
+1
(aq)
+ NO
3
-1
(aq)
+ Na
+1
(aq)
+ Cl
-1
(aq)
Na
+1
(aq)
+ NO
3
-1
(aq)
+ AgCl
(s)

(Spectator Ions)

8. Flame Tests
The flame test is a
procedure used in chemistry
to detect the presence of
certain metal ions, based on
each element's
characteristic emission
spectrum. The color of
flames in general also
depends on temperature.
The flame test is fast and easy to perform, and does not
require any equipment not usually found in a chemistry
laboratory. However, the range of detected elements is
small, and the test relies on the subjective experience of
the experimenter rather than any objective measurements.

9. Samples are usually held on
a nichrome wire cleaned with
hydrochloric acid to remove
traces of previous analytes.
Glass Rod with Nichrome Wire
The test involves introducing
a sample of the element or
compound to a hot, non-luminous
(blue) bunsen flame, and
observing the color that results.
Flame Tests
Flame Test Calcium

10. Sodium is a common component or contaminant in many
compounds and its spectrum tends to dominate over
others. Thus the color yellow overpowers the true color.
The test flame is often viewed through cobalt blue glass
to filter out the yellow of sodium and allow for easier
viewing of other metal ions.
Flame Tests
Sodium - YellowPotassium - Purple Barium - Green

11. Flame Tests
As Arsenic - Blue
B Boron - Bright Green
*Ba Barium - Apple Green
Ca Calcium - Brick Red
Cs Cesium - Pale Violet
Cu(I) Copper(I) - Blue
Cu(II) Copper(II) (non-halide) -
Green
*Cu(II) Copper(II) (halide) -
Blue-Green
*Fe Iron - Gold
In Indium - Blue
*K Potassium - Lilac
Li Lithium – Carmine Red
Mg Magnesium - Brilliant white
Mn(II) Manganese(II) –
Yellowish green
Mo Molybdenum - Yellowish green
*Na Sodium - Intense Yellow
P Phosphorus - Pale bluish green
Pb Lead - Pale green
Rb Rubidium - Pale violet
Sb Antimony - Pale green
Se Selenium - Azure blue
Sr Strontium - Crimson Red
Te Tellurium - Pale green
Tl Thallium - Pure green
Zn Zinc - Bluish Green

12. And Now
for the
Main Event!

13. Mystery of the Thirteen Test Tubes
It was a cold dark night and one of the TAs was
preparing the solutions for this week’s experiment.
The TA had made a key for the unknowns and placed
the key on the lab bench in the stockroom before she
went home for dinner.
While the TA was out, one of the
stockroom workers decided to help
clean the stockroom. (They know
how upset Dr. Bone gets when the
stockroom is a mess!) And – you
know it – the stockroom worker
threw away the key!
So now it is up to you to identify
the contents of the 13 Test
Tubes.
Yeah,
we
know
it’s
cheesy!

14. The Usual Suspects
1.H
2
SO
4
2.K
2
CrO
4
3.Fe(NO
3)
3
4.Na
2S
5.NiSO
4
6.KNO
3
7.Ba(NO
3
)
2
8.NH
3
9.NaCl
10.K
2
C
2
O
4
11.Cu(NO
3
)
2
12.SnCl
2
13.KSCN

15. H
2
SO
4
Bio: Strong Acid, most
powerful industrial chemical in
the world, may produce
insoluble sulfates if “metal”ed
(meddled) with.*
Sulfuric Acid
*Recall #4 of our solubility rules:
All sulfates are soluble except barium,
calcium, strontium, lead (II), and mercury (I).

16. Corrosive; highly exothermic reaction with
water. Burns from sulfuric acid are
potentially more serious than those of
comparable strong acids (e.g. hydrochloric
acid), as there is additional tissue damage
due to dehydration and particularly due to
the heat liberated by the reaction with
water; i.e. secondary thermal damage.
The danger is greater with more
concentrated preparations of sulfuric acid;
however, even the "dilute" ~ 0.1 M H
2
SO
4

will char paper by dehydration if left in
contact for a sufficient while.
MSDS for H
2
SO
4

17. NH
3
Ammonia
A gas with a characteristic
pungent odor. Caustic and
can cause serious health
damage. Exposure to very
high concentrations of
gaseous ammonia can result
in lung damage and death.
Bio: Alias Ammonium Hydroxide (NH
4OH) has
done important work in homes, last known
employment as fertilizer, can turn ugly on
any nosey detectives.

18. K
2
CrO
4
Potassium Chromate
Bio: Best known for its bright disposition,
potassium ion is almost inert, but the
chromate may drop out if faced with
silver, lead or barium. Remains bright even
when it lays low.

19. Potassium Chromate is very toxic and may
be fatal if swallowed. It may also act as a
carcinogen, and can create reproductive
defects if inhaled or swallowed.
K
2
CrO
4
It is also possible that it may react
explosively with other reducing
agents and flammable objects.
It is a strong oxidizing agent.
It may react rapidly, or violently.

20. NaCl
Sodium Chloride
Bio: Nothing but a common salt, almost impossible to
recognize in a crowd, but shows quite a yellow streak
when the real heat is on.*
*i.e., the flame test will
yield a yellow flame.

21. Fe(NO
3
)
3
Ferric Nitrate
Bio: Alias “Iron III” – Ferric is more reactive than
younger brother Ferrous; may be recognized by color
if not confused with other species, can be definitively
identified by “Bloody” encounter with greatest rival
Thiocyanate.*
Ferric
Fe
3+
Ferrous
Fe
2+
(*More about that in the KSCN slide.)

22. K
2
C
2
O
4
Bio: Actions not well known, but moderate
toxicity noted, handle with care, believed
to have a falling out with “Barium”.
Potassium Oxalate

23. Na
2
S
Sodium Sulfide
Bio: Alias “Le Pew”, a
real loner, possible
messy confrontations
with copper, ferric,
nickel or tin; tends to
linger on the skin if
touched.
(Do NOT Touch!)
Caution: Na
2S + H
2SO
4
yields which smelly gas?

24. Cu(NO
3
)
2
Cupric Nitrate
Bio: First name officially changed
to “Copper II”; leading chemical
citizen, many business ventures
include electrical wire
manufacturing and production of
alloys, notably brass; in solution is
easily recognizable by “melancholy”
(sad or blue) disposition.
Note: Once suspected of conspiring
with ammonia to impersonate blue ink.

25. NiSO
4
Nickel Sulfate
Caution: Nickel salts are
considered carcinogenic.
Bio: Once very valuable, now net worth greatly
reduced, “Nick” is easily recognized by his “envious”
(green) nature.

26. SnCl
2
Stannous Chloride
Bio: a.k.a. Tin Chloride, a hard worker, known since
ancient times, currently employed in food packaging
industry, recyclable; fluoride form prevents tooth
decay; somewhat acidic personality; unfortunate
confrontation with “Le Pew”.
Note: Stannous Chloride was
prepared in 1 M HCl, so it will
appear quite acidic.

27. Solutions of tin ( II) chloride can also serve simply as
a source of Sn
2+
ions, which can form other tin (II)
compounds via precipitation reactions, for example
brown (or black) tin (II) sulfide:
Unfortunate Confrontation
with “Le Pew”
SnCl
2
(aq) + Na
2
S(aq) → SnS(s) + 2 NaCl(aq)
stannous sulfide (′stan·əs ′səl′fīd) SnS Dark crystals; insoluble in
water, soluble (with decomposition) in concentrated hydrochloric
acid; melts at 880°C; used as an analytical reagent and catalyst,
and in bearing material.
Also known as tin monosulfide; tin protosulfide; tin sulfide.

28. KNO
3
Potassium Nitrate
Bio: The “Most Boring” substance known
outside of the noble gasses, chronically
unemployed, does not participate in
chemical reactions but often “watches”.
Can be distinguished from the
other “common salt” by its pale
violet response to any “trial by
fire.”

29. While potassium nitrate may be boring in solution, the solid is a
critical oxidizing component of black powder gunpowder. In the past
it was also used for burning fuse technologies including slow
matches.
It readily precipitates and was widely "harvested" since the Late
Middle Ages and Early Modern era through the 19th century from
urine from which it was forced to crystallize in various odorous
ways. Its common names include saltpeter, American English
saltpeter, & Nitrate of potash.
KNO
3 (aq)
KNO
3 (s)

30. KSCN
Potassium Thiocyanate
Bio: Poisonous little creature, approach
with caution, longstanding “blood” feud
with the Iron Brothers.
*Note: It may appear black in the well,
use a toothpick to smear some on a piece
of filter paper to verify color. KSCN + FeCl
3
Chemists are always trying to make
mimics of the Chemicals found in
nature. We can do this by mixing
Iron(III) compounds with potassium
Thiocyanate. The Chemical we get is
similar to the Iron-containing part of
hemoglobin and is a blood red color.*

31. Ba(NO
3
)
2
Barium Nitrate
Bio: Little known on this one, chance
encounters with sulfuric acid have often
“precipitated” pale consequences.
Toxic by ingestion or inhalation. Symptoms of poisoning
include tightness of muscles (especially in the face and neck),
vomiting, diarrhea, abdominal pain, muscular tremors, anxiety,
weakness, labored breathing, cardiac irregularity, and
convulsions. Death may result from cardiac or respiratory
failure, and usually occurs a few hours to a few days following
exposure to the compound. Barium nitrate may also cause
kidney damage.

32. The NITRATES
are
a red herring.
Lead in the
Wrong Direction

33. Midterm Exam (Feb. 23-26)
Exam Review
Thursday – Feb. 19
7-9 pm in G3.
For March 3-6
Read: Radiochemistry - You will need the Green Book for this
experiment. (It may be purchased for $10.00 cash or check
in Room 142 Schrenk.)
Good
Luck!
Due: 13 Test Tubes (pp 109-114)* - You may turn in the lab
either the week of Feb. 23-26 or Mar. 3-6.
*This material will be on the midterm exam, so you should
answer the post lab questions prior to the exam.