posted by Gilbert on .
Woiuld you expect jewelry made from an alloy of silver and copper to tarnish (oxidize) in a laboratory where fumes of bromine are present?
I think that it wouldn't because the bromine fumes are probably not ions, and even if they were they would not react because they are less easily reduced than silver and copper. But I'm not sure, so thanks for anyone's help.
I would expect them to tarnish. While it is true that Br2 fumes are not ionic (you are correct about that) they will tarnish because of another fact; i.e., both CuS and Ag2S are VERY insoluble (they are solid precipitates) so the driving force from the formation of CuS or Ag2S is very strong. I also realize this is not in solution but we are talking about a very think layer of Ag2Br or CuS and that thin layer is the "tarnish."
I'm probably too late but DrBob probably didn't give you the right answer. Both silver and copper reduce bromine, so that means that bromine oxidizes both these metals. The oxidation of the silver and copper would cause the jewelry to tarnish.
On a table of oxidation and reduction, Bromine is the oxidizing agent and is higher on the table than both Copper and Silver. According to the spontaneity rule (if Oxidizing Agent is higher than the reducing agent there is a reaction) this would mean that the bromine would in fact tarnish (oxidize) the jewellery.