Silver Alloy labSilver Alloy lab

PurposePurpose

To determine the % by mass of Ag in To determine the % by mass of Ag in sterling silversterling silver

Also… To practice quantitative Also… To practice quantitative Chemistry separation methodsChemistry separation methods

Quantitative lab method—to determine amounts presentQuantitative lab method—to determine amounts present Qualitative lab method—to determine presence or absenceQualitative lab method—to determine presence or absence

To separate AgTo separate Ag++

Ag will be dissolved (turned into AgAg will be dissolved (turned into Ag++) ) from sterling silver using nitric acid.from sterling silver using nitric acid.

Since AgCl is insoluble, add ClSince AgCl is insoluble, add Cl-- to the to the solution and Agsolution and Ag++ precipitatesprecipitates out as out as AgClAgCl

Most metal chlorides are soluble Most metal chlorides are soluble (except those of Ag, Hg, Pb), so ALL (except those of Ag, Hg, Pb), so ALL other metal ions stay in solutionother metal ions stay in solution

Note: Could also use INote: Could also use I-- or Br or Br--

OverallOverall1.1. Clean and set up the lab equipmentClean and set up the lab equipment

2.2. Weigh your alloy sampleWeigh your alloy sample

3.3. Dissolve the alloy in acidDissolve the alloy in acidMetals + Metals + HNOHNO33 Metal(NO Metal(NO33))(aq) (aq) + H+ H22O + NOO + NO(g)(g)

4.4. Precipitate the SilverPrecipitate the SilverMetal(NOMetal(NO33))(aq) (aq) + + NaClNaCl(aq)(aq) NaNO NaNO3(aq)3(aq) + Metal(Cl) + Metal(Cl)Since silver chloride is insoluble, it will crystallize out (overnight)Since silver chloride is insoluble, it will crystallize out (overnight)

But, copper chloride will remain aqueousBut, copper chloride will remain aqueous

5.5. Filter out the AgCl madeFilter out the AgCl made

6.6. Dry and weigh the AgCl Dry and weigh the AgCl

7.7. Calculate the mass of Ag (in AgCl) and then Calculate the mass of Ag (in AgCl) and then determine the % Ag in your original sampledetermine the % Ag in your original sample

We’re actually

doing #1-4 tomorrow

Add to your procedure:Add to your procedure:

8. Calculate the percentage error of 8. Calculate the percentage error of your result… Sterling silver is 92.5% your result… Sterling silver is 92.5% silversilver

Mass of sterling sample g

Mass of NaCl needed g

Mass of labeled filter + dish g

Mass of filter + dish + AgCl g

Mass of AgCl g

Mass of Ag in AgCl g

% Ag in Sterling %

% Error %

Data TableData Table

You must show your

work for all

calculations in an analysis section

Write-upWrite-up

Purpose QuestionPurpose Question Data Collection and Analysis:Data Collection and Analysis:

Data Table (include qualitative observations)Data Table (include qualitative observations) CalculationsCalculations

Conclusion and Evaluation:Conclusion and Evaluation: ConclusionConclusion Sources of Error with HOW each would affect Sources of Error with HOW each would affect

the datathe data ImprovementsImprovements