silver tarnish is the result of slver metal reacting with sulfur compounds, such

Question

silver tarnish is the result of slver metal reacting with sulfur compounds, such as H2S, in the air. the tarnish on silverware (Ag2S) can be removed by soaking in a solution of NaHCO3(baking soda) in a basin lined with aluminum foil.

1/ write a balanced equation for the tarnishing of Ag2S. do not include phases

2/ how many electrons are transferred per mole of silver ??

3/ write a balanced reaction for the reaction of Ag2S with Al metal and H2O to produce Al(OH)3,H2S, and Ag metal. do not include phases

Explanation / Answer

(1) Ag is oxidized by O2 in the air, and then combines with H2S to form Ag2S

4 Ag + 2 H2S + O2 => 2 Ag2S + 2 H2O


(2) Oxidation half reaction: Ag => Ag+ + e-

Number of electrons transferred per mole of Ag

= 1 mole of electrons (or 6.02 x 10^23 electrons)


(3) Oxidation: 2 Al + 6 H2O => 2 Al(OH)3 + 6 H+ + 6 e-

Reduction: 3 Ag2S + 6 e- => 6 Ag + 3 S2-


Add Oxidation + Reduction and cancel electrons to get:

3 Ag2S + 2 Al + 6 H2O => 2 Al(OH)3 + 3 H2S + 6 Ag

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