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How Much is a Penny Worth?
Percentage Copper in a U.S. One-Cent Coin A Quantitative Analysis
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The U.S. Penny Mass of penny, if only Cu, worth >$0.01
Modern penny is ~2.5% copper clad Knowledge of composition important to prevent hoarding and selling for metal Gravimetric analysis of recovered copper just one way
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The Assay mpenny is easy mcopper is a little harder
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The Process Obtain and weigh a penny… …and dissolve it in acid:
Zn(s) + HCl(aq) ZnCl2(aq) + H2(g) Cu(s) + HNO3(aq) Cu(NO3)2(aq) + NO2(g) ↑Unbalanced! ↓ Do this reaction in the hood, please CAUTION! 6 M HNO3 and 12 M HCl are corrosive to metals. They’re also corrosive to skin and clothes. Any spills must be wiped up immediately
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The Process Remove nitrate… Reduce the acidity by reducing volume
Boil to convert Cl- to Cl2 and NO3- to NO2 NO Cl- Cl2(g) + NO2(g) unbalanced! Reduce the acidity by reducing volume But solution is still too acidic But solution is still too acidic Do this reaction in the hood, please
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HNO3(aq) + H3NSO3(aq) → H2SO4(aq) + N2O(g) + H2O(l)
The Process Deplete remaining HNO3… HNO3(aq) + H3NSO3(aq) → H2SO4(aq) + N2O(g) + H2O(l) Boil to speed the reaction, then… … dilute to 50 mL Do this reaction in the hood, please
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The Process Convert Cu2+ to Cu+… Add FeSO4 in excess
Cu Fe2+ Cu Fe3+ Precipitate Cu+ as CuSCN(s)… Cu SCN- CuSCN Side reaction that must be considered… Fe SCN- FeSCN2+
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The Process Recover the Cu by vacuum filtration
Rinse the beaker and filter paper with dilute KSCN Rinse the filter paper with ice-cold water Eliminate water with ethanol Dry at 80º for 30 min
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REVIEW The Process Dissolve a weighed penny
Eliminate nitrate (2 steps) Reduce Cu2+ to Cu+ REVIEW Precipitate Cu+ as CuSCN, convert Fe3+ to FeSCN2+ Recover the CuSCN by vacuum filtration Dry at 80º, weigh
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This investigation, Author
1: Introduction and Conclusion 2: Discussion 3: Data/Results and Experimental A: Introduction, Conclusion, Data/Results B: Discussion and Experimental
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