Percent Composition of a Penny , Lab Reports of Chemistry

Download Percent Composition of a Penny and more Lab Reports Chemistry in PDF only on Docsity! 7-4 Percent Composition of a Penny Background Information: For the first time in U.S. history, the cost of manufacturing both a penny and a nickel is more than the 1-cent and 5-cent values of the coins themselves. Skyrocketing metals prices are behind the increase, the U.S. Mint said in a letter to members of Congress last week. The Mint estimates it will cost 1.23 cents per penny and 5.73 cents per nickel this fiscal year, which ends Sept. 30. The cost of producing a penny has risen 27% in the last year, while nickel manufacturing costs have risen 19%. (From USA Today 5/16/2006) Post 1983 pennies have a copper jacket and a zinc core. We hope to determine the percent composition of the penny. Find % Copper and % Zinc. This will be done by reacting zinc with hydrochloric acid to from zinc ions in a single replacement reaction. The acid reacts with the zinc but not the copper. The reaction of zinc metal with the hydrochloric acid (HCl) produces zinc but not the copper. The reaction of zinc metal with hydrochloric acid produces zinc chloride and hydrogen gas. Safety: ***Wear safety goggles and protective gloves *** If you spill the HCl on yourself, rinse with water *** Materials: post 1983 penny 50 ml beaker file mass balance 3 M HCl metal forceps/tweezer Procedure: DAY 1 Using a file etch an “X” on one side of the penny. Also etch a notch on the edge in the four positions shown in the diagram. 1. Place the penny on the balance and record the mass of the penny (in grams) DO NOT PUSH ON THE BALANCE PAN, IT WILL RUIN THE BALANCE. 2. Use your phone to take a picture of your penny. 3. In a 50 ml beaker (or what is available) pour approximately 60 ml of HCl ( The beakers may already be filled for you) 4. Mark your beaker (use a piece of paper and tape to label your beaker) 5. Place the penny in the beaker etched side up 6. Place the beaker with the acid and penny in the evacuation hood. 7. Observe the reactions. DAY 2 1. Half fill a second beaker (100 ml or 200 ml) with water. 2. Using the forceps remove the penny from the beaker and place it in the water beaker 3. Put the beaker containing the acid in the evacuation hood 4. Lay penny on a paper towel to get the majority of water off of the penny. 5. Put your name on the paper towel and place it in the lab somewhere that you can find it the next day. DAY 3 1. Find your penny and measure the mass of the penny using the balance (measure in grams), record the mass. SEE THE BACK FOR FURTHER INFORMATION The Composition of the Cent Following is a brief chronology of the metal composition of the cent coin (penny):  The composition was pure copper from 1793 to 1837.  From 1837 to 1857, the cent was made of bronze (95 percent copper, and five percent tin and zinc).  From 1857, the cent was 88 percent copper and 12 percent nickel, giving the coin a whitish appearance.  The cent was again bronze (95 percent copper, and five percent tin and zinc) from 1864 to 1962. (Note: In 1943, the coin's composition was changed to zinc-coated steel. This change was only for the year 1943 and was due to the critical use of copper for the war effort. However, a limited number of copper pennies were minted that year.)  In 1962, the cent's tin content, which was quite small, was removed. That made the metal composition of the cent 95 percent copper and 5 percent zinc.  The alloy remained 95 percent copper and 5 percent zinc until 1982, when the composition was changed to 97.5 percent zinc and 2.5 percent copper (copper-plated zinc). Cents of both compositions appeared in that year. CURRENT METAL VALUES Zinc (Density of Zinc =7.13 g/cc) Copper (Density of Copper = 8.96 g/cc) Source: http://vincentmetals.com/Daily_Zinc_Prices.html