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Silver Alloy lab. Purpose. To determine the % by mass of Ag in sterling silver Also… To practice quantitative Chemistry separation methods Quantitative lab method—to determine amounts present Qualitative lab method—to determine presence or absence. To separate Ag +.
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Purpose • To determine the % by mass of Ag in sterling silver • Also… To practice quantitative Chemistry separation methods • Quantitative lab method—to determine amounts present • Qualitative lab method—to determine presence or absence
To separate Ag+ • Ag will be dissolved (turned into Ag+) from sterling silver using nitric acid. • Since AgCl is insoluble, add Cl- to the solution and Ag+precipitates out as AgCl • Most metal chlorides are soluble (except those of Ag, Hg, Pb), so ALL other metal ions stay in solution • Note: Could also use I- or Br-
We’re actually doing #1-4 tomorrow Overall • Clean and set up the lab equipment • Weigh your alloy sample • Dissolve the alloy in acid Metals + HNO3 Metal(NO3)(aq) + H2O + NO(g) • Precipitate the Silver Metal(NO3)(aq) + NaCl(aq) NaNO3(aq) + Metal(Cl) Since silver chloride is insoluble, it will crystallize out (overnight) But, copper chloride will remain aqueous • Filter out the AgCl made • Dry and weigh the AgCl • Calculate the mass of Ag (in AgCl) and then determine the % Ag in your original sample
Add to your procedure: 8. Calculate the percentage error of your result… Sterling silver is 92.5% silver
Data Table You must show your work for all calculations in an analysis section
Write-up • Purpose Question • Data Collection and Analysis: • Data Table (include qualitative observations) • Calculations • Conclusion and Evaluation: • Conclusion • Sources of Error with HOW each would affect the data • Improvements