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Analyzing the Composition of a US Penny: A Quantitative Study

This article aims to determine the percentage of copper in a US penny through a comprehensive quantitative analysis. It explores the importance of understanding the coin's composition to prevent hoarding and selling for metal. The process involves obtaining, dissolving, and analyzing the penny using various chemical reactions.

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Analyzing the Composition of a US Penny: A Quantitative Study

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  1. How Much is a Penny Worth? Percentage Copper in a U.S. One-Cent Coin A Quantitative Analysis

  2. 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

  3. The Assay mpenny is easy mcopper is a little harder

  4. 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

  5. The Process Remove nitrate… Boil to convert Cl- to Cl2 and NO3- to NO2 NO3- + Cl- Cl2(g) + NO2(g) unbalanced! But solution is still too acidic But solution is still too acidic Reduce the acidity by reducing volume Do this reaction in the hood, please

  6. 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

  7. The Process Convert Cu2+ to Cu+… Add FeSO4 in excess Cu2+ + Fe2+Cu+ + Fe3+ Precipitate Cu+as CuSCN(s)… Cu+ + SCN- CuSCN Side reaction that must be considered… Fe3+ + SCN- FeSCN2+

  8. 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

  9. The Process Dissolve a weighed penny Recover the CuSCN by vacuum filtration Eliminate nitrate (2 steps) Reduce Cu2+ to Cu+ REVIEW Precipitate Cu+ as CuSCN, convert Fe3+ to FeSCN2+ Dry at 80º, weigh

  10. This investigation, Author 1: Introduction and Conclusion 2: Discussion 3: Data/Results and Experimental This investigation, Author A: Introduction, Conclusion, Data/Results B: Discussion and Experimental

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