How Many Moles of Zinc Are in a Penny?

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How many moles of zinc are in a penny? Purpose: This lab is being performed so students can visualize a single-replacement reaction and calculate how much zinc is in a post-1982 penny. Materials: A post- 1982 penny steel wool 3 M HCl graduated cylinder small beaker tongs balance paper towels sharp edge Safety: 3 M hydrochloric acid (HCl) is fairly caustic. Wash hands immediately if you spill on them. Wear goggles. Procedure: 1. Clean off penny with steel wool 2. Use a file and cut a small groove into two edges of the penny. Opposite sides works well. 3. Use a sharp object and CAREFULLY cut an “X” on one side of the penny until you see the zinc. 4. Mass the penny. 5. Place the penny in 20 mL of 3 M HCl that is in a small beaker. Put the “X” side up. 6. If you use the tongs, PLEASE wash them because the acid will continue to react with them overnight. 7. Let the penny sit overnight. If you do not see bubbles, something is wrong. Write down your observations. 8. After the penny is finished reacting, using tongs, remove the penny. 9. Wash off the penny in tap water carefully and thoroughly. You will be holding the pennies with your fingers and if you still have acid in or on them, it can be uncomfortable. 10. Dry off the penny carefully. 11. Mass the penny again. 12. Calculate how much zinc left the penny. Post this number on the board. Calculations: (do rough drafts of calculations in your lab notebook. Your formal report should have very well organized, well labeled, calculations.) 1. Show all calculations. Set-up in words is encouraged. 2. Calculate how much (in g) zinc left the penny 3. Calculate the class’s average for amount of zinc in a penny. Use the class average value for amount of zinc when you do future calculations. It is hoped that the class’s average is a better representation of the amount of

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