Will the nitric acid in the wash water interfere with the weight of the silver chloride?I'm doing the common AP Chemistry: Analysis of Ag in an Alloy Lab. If this lab is unfamiliar, it is basically...

Will the nitric acid in the wash water interfere with the weight of the silver chloride?

I'm doing the common AP Chemistry: Analysis of Ag in an Alloy Lab.

If this lab is unfamiliar, it is basically finding the mass of the silver in the alloy by precipitating the alloy with NaCl to form AgCl, then measuring the amount of Ag in AgCl.

Here's a link to the lab: http://chemistryrocks.net/AP%20Chem%20Labs/Analysis%20of%20Ag%20in%20an%20Alloy.pdf

Asked on by polisciman

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ndnordic's profile pic

ndnordic | High School Teacher | (Level 2) Associate Educator

Posted on

the nitric acid will not interfere with your analysis to find the mass of silver in the alloy.

Some of the nitric acid is used to oxidize the Ag and Cu to their +1 and +2 states respectively, forming nitrate salts with each of the metal ions.  The nitrate ions that oxidize the metals are reduced to NO (g).

When the NaCl is added the silver ions combine with the chloride ions to form a precipitate of AgCl (s), which will be filtered and washed.  Since copper chloride and copper nitrate are both soluble, the copper remains in solution.  Any free nitric acid will be washed away when you rinse the precipitate. so that only AgCl is remaining. As long as you dry the AgCl to constant weight you should get the correct result.

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