silver
❖The Latin name of silver is Argentum
which means white. Silver is very
important metal having ornamental
value.
❖Silver is abundant in mineral rich soils.It
is available in mixed form, generally in
crystal form.
Symbol Ag
Latin name Argentum
Atomic number 47
Atomic mass 107.9 amu
Valency 1
Electronic [Kr]4d105s1
configuration
Key isotopes 107
Ag,109Ag
Occurrence Of silver
Silver is found in native state as well as
in combined state. In native state, it is
found in USA, Mexico,Canada, etc. It is
found in combined state as sulphide and
chloride.
➢ Ores of silver
I. Argentite or silver glance (Ag2S)
II. Silver copper glance (CuAg)2S2
III. Horn silver (AgCl)
IV. Argentiferous galena (PbS. Ag2S)
V. Pyrargyrite or ruby silver 3Ag2SbS3
The main producers of Ag are Mexico
,USA, Peru, Canada, Australia, Russia
and Chile.
extractiOn Of silver frOm
argentite Ore using cyanide
PrOcess
This method is also called Mac-
Arthur-Forrest process.
Theory:
Ag2S present in the argentite ore is
converted into solution of sodium
argentocyanide (Sodium
dicyanoargentate(I)) by treating
ore with dilute NACN solution.
Ag2S + 4NaCN ⇌ 2Na[Ag(CN)2] + Na2S
Sodium dicyanoargentate(I)
Sodium argentocyanide solution thus
obtained on the treatment with zinc gives
metallic silver as
precipitate.
2 Na[Ag (CN)2]+ Zn ⇌ Na2[Zn(CN)4] + Ag↓
Sodium tetracyanozincate(II)
❖ Steps involved in the
metallurgy
d)a Crushing and pulverization:
Big lumps of ore are crushed using jaw
crushers to get crushed ore which are
pulverized (powdered) using
pulverisers or ball mills to get
powdered ore.
d)b Concentration of ore by froth-
floatation process:
Powdered ore is dipped into a tank
containing water and small quantity of
pine oil. The mixture is agitated by
using blast of air. Gangue particles are
wetted by water and get collected at
the bottom of the tank. The ore
particles being preferentially wetted
by oil come on the surface in the form
of froth. The froth is skimmed out to
collect the concentrated ore.
Fig: Concentration of ore by froth floatation process
c) Formation of complex
cyanide: Concentrated ore is agitated
with dilute sodium cyanide
solution (0.5%) using a current of air.
Then solution of sodium
argentocyanide is obtained.
Ag2S + 4NaCN ⇌ 2Na[Ag(CN)2] + Na2S
Sodium argentocyanide
Due to the case that reaction is
reversible, air is blown, which removes
Na2S from equilibrium
mixture as Na2SO4. So reaction
proceeds in forward direction.
2Na2S + H2O + 2O2 → Na2S2O3 + 2NaOH
Na2S2O3 + 2NaOH + 2O2 → 2Na2SO4 + H2O
2Na2S + 4O2 → 2Na2SO4
Or, Na2S + 2O2 → Na2SO4
Even if ore is horn silver, same process
can be carried out.
AgCl + 2NaCN → Na[Ag(CN)2] + NaCl
d) Reduction by precipitation
method: The solution obtained
from the above method is filtered
off and treated with finely divided Zn
where Ag will be precipitated in the
form of dark amorphous powder.
2Na[Ag(CN)2] + Zn → 2Ag↓+ Na2[Zn(CN)4]
This precipitate of silver is removed
by filtration process and the
precipitate is dried out.
e) Purification of silver
Steps:
I. Dried silver is heated with
KNO3 solid in crucible to get a
compact mass. The impurities
are oxidized on the surface.
Liquid silver forms compact
mass on cooling.
II. Then impure silver (containing
Cu, Al, etc.) is purified by
electrolysis. Impure silver is
made anode and pure silver is
made cathode. 6% AgNO3
solution acidified with 1%
HNO3 is used as electrolyte.
On passing D.C. silver
dissolves from anode and gets
collected at cathode.
The reactions take place as
follows:
At anode: As → Ag+ + e-
At cathode: Ag+(aq.) + e- → Ag(s)
[Cupellation may also be used
if Pb is suspected. In this
process, Pb is blown away by
air in the form of PbO]
PrOPerties Of silver
Physical properties:
1. Silver metal is white in colour.
Alchemist used the term luna for
silver which means moon.
2. Silver is good conductor of heat
and electricity. Due to its good
conductance, it is used to prepare
electrode.
3. Silver is malleable and ductile.
4. The density of silver is 10.52
gram per cc.
5. Melting point of silver is 9560C
and boiling point is 19550C.
Chemical properties:
1. Action with air:
Silver is not chemically active
metal. Therefore, under
ordinary condition, it does not
react with air. However, it is
tarnished by air containing even
traces quantity of hydrogen
sulphide.
2Ag + H2S → Ag2S↓ + H2
Black ppt
Due to hydrogen sulphide
pollution, silver monuments are
being tarnished. This demands
regular cleaning of silver wares.
2. Action with acids:
Silver lies below hydrogen in
electrochemical series. So it
cannot displace
hydrogen gas from dilute,
mineral and non-oxidizing acids
such as HCl, H2SO4. However,
silver reacts with concentrated
nitric acid and concentrated
sulphuric acid as follows:
2Ag + 2H2SO4 → Ag2SO4↓ + SO2↑ + H2O
3Ag + 4HNO3 (conc.) →3AgNO3 + 2H2O + NO
Ag + 2HNO3 (dilute)→ AgNO3 + H2O + NO2
3. Action with non-metals:
Some non-metals such as
sulphur, chlorine, etc. react
with silver on heating to form
corresponding compounds.
2Ag + S + heat → Ag2S
2Ag + Cl2 + heat →2AgCl
uses Of silver
A. In the early days silver
were used to prepare coins.
An alloy of silver and copper
is used to prepare coins.
Hence, it is regarded as
coinage metal.
B. It is used to prepare
electrodes.
C. It is used in photography.
D. It is used for electrical
purposes.
E. It is used to prepare
jewellery.
F. It is used to prepare alloy.
silver nitrate (AgNO3)
Name Silver (I)
nitrate
Molecular 169.87
mass
Colour White
Melting 209.7oC
point
Boiling 440oC
point
Solubility 256 gram per
100mL at 25oC
Hazards Corrosive,
explosively
reacts
with ethanol
PREPARATION:
Silver nitrate can be
prepared by the action of
nitric acid on silver.
3Ag + 4HNO3 (cold and dilute) →
3AgNO3 + 2H2O + NO
Ag + 2HNO3 (hot and conc.) → AgNO3 +
H2O+ NO2
These reactions should be
carried out in fume cupboard
or fumehood to expell the
toxic nitrogen oxide gases.
USES:
A. It is used as
laboratory reagent. For
example, it is used for
halide test (Cl ̄, Br ̄, I ̄)
B. It is used in silvering
of mirror.
C. It is used to prepare
indelible ink.
D. It is used to prepare
some silver based
explosives such as silver
acetylide, silver
fulminate, silver azide,
etc.
E. It is used in the
preparation of
photographic film where
silver nitrate is reacted
with sodium or patassium
salts.
F. It is used to prepare
Tollen's reagent.
silver
chlOride(AgCl)
PREPARATION:
Silver chloride can be
easily prepared by adding
the solution of a soluble
chloride to the solution of
silver nitrate in dark.
AgNO3(aq.) + KCl(aq.)→
AgCl(s)+KNO3
The precipitate is
separated by filtration,
washed and dried at
about 70oC.
USES:
i. Silver halides are
sensitive to light,so
these are used in
photography. Silver
chloride is used for
making photographic
paper.
