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… 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

6. 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

7. 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+

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. 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

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