Download silver tarnish

SILVER TARNISH
——A Redox Reaction
overview
• Tarnish, which appears as black or
brown streaks and patches on silver
ware, is silver sulfide, a compound
formed when silver interacts with sulfur
in the air.
chemical equation
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0
0
+1
-2
4 Ag + O2 + 2 H2S → 2 Ag2S + 2 H2O
Ag 0--+1 lose electron ,oxidized, reducing agent.
O 0__-2 gain electrons, reduced, oxidizing agent.
2Al+3Ag2S+6H2O→6Ag+2Al(OH)3+3H2S0
0
1
3
0
Al 0_+3 lose electron ,oxidized, reducing agent.
Ag 1__0 gain electron ,reduced, oxidizing agent.
Other equation about
silver
• In one of the most famous reactions in
chemistry, addition of colorless aqueous
silver nitrate to an equally colorless
solution of sodium chloride produces an
opaque white precipitate of AgCl:[3]
• Ag+(aq) + Cl−(aq) → AgCl(s)
• This conversion is a common test for the
presence of chloride in solution. Due to
its conspicuousness it is easily used in
titration.
Rust Protection
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1. Change the internal origination of the metal. Like adding chromium,
nickel to common steel can make stainless steel
2. Cover mulch on the surface of metal.
3. Dispose with corrosive.
4. Connect metal with reactive metal, when electrochemical corrosion
happens, the reactive metals go through oxidizing reaction and
prevent metal from corrosion
5. Connect metal with negative electrode, and then connect a
conductive inert material with positive electrode.
reaction between
silver and acid
• sequence of simple metal activity
•
Cs、 Rb、 K、Ba 、 Ca、 Na 、Mg 、Mn、 Zn、 Cr 、Fe 、Co 、Ni、
(H2)、 Cu、 Hg 、Ag、 Rh 、Pd 、Pt 、Au
• 3Ag+4HNO3=3AgNO3+NO↑+ 2H2O
2Ag + 2H2SO4 （concentrated）=Ag2SO4 +
SO2↑ + 2H2O
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factors affecting silver tarnish
It is recognized that more pure the silver is,
the easier it is eroded.
The silver often is alloy with copper or
other metals. Their electric potential is
different, under certain conditions; it will act
like a reaction occurs inside the battery and
eroded copper and also silver.
For other factors, such as the concentrate
of sulfuret and radiations such as ultraviolet
affect the tarnish.