The percent composition of copper was analyzed for both pre and post 1982 pennies. Lab determination of the percent composition of a penny via a redox reaction. The new penny is made of a metal composition of 97. In 1982 the composition of the penny was changed from being one of nearly pure copper to that of a zinc. Ib chemistry experiment 4 composition of a post1983 penny lab report background. The penny lab students will design a collect data evidence. Percent composition tells you by mass what percent of each element is present in a compound. Before 1982, pennies contained about 95% copper and 5% zinc. Percent composition is the term used to describe the percent by mass of each element in a compound. A chemical reaction is the change of substance into a new one that has a different chemical identity. We hope to determine the percent composition of these two metals present in a penny. Post1983 pennies have a copper jacket and a zinc core. It is usually followed by easily observes physical effect. Express your answer as the number of pre1982 and post1982 pennies in the container.
The experiment will be using hcl a strong acid to dissolve all the zinc. The percent composition is used to describe the percentage of each element in a compound. The rest was tin andor zinc depending on the year of issue. The percent composition can be found by dividing the mass of each component by total mass. During world war ii the composition of the penny was changed from 95 percent copper and 5 percent zinc and tin to zinccoated steel because copper was needed for war efforts. After plotting these data, a linear trendline is applied, fitting the equation y 3.
Then use excel to calculate the percent copper of pennies from the calculated average densities of pure copper and pure zinc that you measured. Burner was ignited using a flint lighter to heat up the crucible containing the magnesium ribbon with the cover on discussion introduction purpose percentage composition involves determining the percentages of elements in. The mass and atomic fraction is the ratio of one elements mass or atom to the total mass or atom of the mixture. Data table 1 trial mass of 10 pennies made before 1982 mass of 10 pennies made after 1982 1 123. Not enough scores, penny not all reacted, not left to soak long enough. To determine the isotopic composition of the element coinium without opening the container. Heres a good template for your conclusion for your penny lab. It is typically found using the molar mass values for both the elements in the compound and the compound itself. What property of the element coinium is different in its pre1982 and post1982 forms. The general form for this lab is the same as earlier this term. Isotopic pennies prelab read the lab handout carefully and answer the following questions. Chemistry laboratory percent composition of a penny page 2. The percentage composition of a compound is the percentage by mass of each of the elements in the compound.
The outside is certainly made of copper, but thats not the whole story. The hollow penny introduction pennies are made of copper, arent they. The lincoln penny has undergone numerous design changes as well as changes in composition. Your job is to work with your group to determine the percent composition of a post1982 penny. This lab introduces the concept of density and uses it to. Also, notch the edge of the penny at four places 90o to each other. Furthermore, the current penny is often referred to as a zincoln. Place the penny in the hcl solution etch side up and record observations for 35 minutes. View lab report chem lab 12 from biology biology at university of texas. If the zinc is not fully exposed, not all of it reacts, thus turning the solution slightly yellow. Plot of the density of cuzn composites verses composition.
Oxidation involves the gain of electrons of hydrogen or the loss of oxygen or decrease in oxidation state. In this lab, we will determine the percent composition of a modern post1982 penny by using a strong acid to react and dissolve the zinc core, leaving only the copper coating. For example, in the first one, you will find the total molar mass. Penny metal composition by year coin collecting enterprises. Chem lab 12 maribel pacheco chem 140531430 experiment. Pennies were being melted down for the value of their metal.
In this penny lab, students determine the percent composition of a penny produced after 1982. Take a post1983 penny and, using a triangular file, lightly etch an x on one side of the penny. Calculate the percent composition of the element coinium from your data. Measuring the density of pre1982 and post1982 pennies. Sep, 2014 step by step solution to find % cu in a penny when you know the total weight of coin and the molar amount of copper. Id like to put this up to provide you with guidance, to make the rest of your lab conclusions first rate. In 1982 the composition of pennies was changed because they contained more than 1 cents worth of copper. Percent composition penny lab chemistry physical sciences. The purpose of this lab is to accurately determine. After 1982, however, the composition of pennies was changed to contain mostly zinc and only a small amount of copper. The purpose of this experiment is to determine the percent composition of a modern post1982 penny by using a strong acid to react and dissolve the zinc core, leaving only the copper coating. The purpose of this lab is to accurately determine the densities of pre1982 and post1982 pennies. Background pennies dated up to 1981 are made of copper. Percent mass of element x grams of element x grams of the compound.
Basically, all we had to do was weigh a penny from before 1982. It is surprising that it took so many steps, using very exotic methods, in order to get a seemingly simple answer. To determine the percent composition of cu and zn in a penny. This was determined by iodometric titration analysis. The purpose of the lab was to dissolve copper salt in water with an excess of aluminum. They calculate the amount of copper and zinc in the penny by performing a chemical reaction on the penny with hydrochloric acid. Then, the students need to calculate the average percent composition of each color. Determination of % composition of pennies using redox and double displacement precipitation reactions introduction. Now i have no idea what to do and i dont have anyones contact information in my class, so i was hoping i could find help here. Determining the mass percent composition in an aqueous. In order to determine the mass of each metal in a penny, the metals are separated by chemical reaction.
Mass percent of carbon in sodium bicarbonate scientific. Percent mass of copper in a penny introduction the purpose of this lab is to determine the percent mass of cu in a penny and see if the fabricator that makes the planchets for the government is using the correct amounts of cu in the pennies. Mass percent of carbon in sodium bicarbonate continued 5 21 inn scientific nc ihts esered acknowledgment special thanks to dewayne lieneman, retired, glenbard south high school, glen ellyn, il, for sharing this activity with flinn scientific. Once only copper remains, compare its mass to the entire mass of the penny to determine how much of a penny is copper and how much is zinc. This merges the word zinc with lincoln since pennies today are called lincoln cents. Mar 27, 2014 the determination of copper in pennies by. Sample traditional lab report density of pennies hypothesis based on the instructions provided the density of pennies made before 1982 will be greater than the density of pennies made after 1982. Chemistry midterm all lab purpose and errors flashcards. Lab hydrolysis of water in an electrochemical cell.
The composition was changed in 1982 because the cost of making the penny was more than the. What measurable property distinguishes a pre82 penny from a post82 penny. In what ways is the penny mixture a good analogy, or model, for actual element isotopes. If you shaved the edge of the penny, this will not fully expose the zinc and it will also make the mass of the copper smaller. Pennies since 1982, however, are made up mostly of zinc. Percent composition worksheet solutions find the percent compositions of all of the elements in the following compounds. In their lab group students determine the percent composition of.
Density and percent compositions chemistry libretexts. The zinc which was already silver coated the penny. I measured 30 old pre1982 us pennies mass and volume and plotted that data on a graph. A brief history of the us onecent coin penny composition. Along with that information, i found a website that discussed the composition, mass, and density of a penny. Percent composition of hydrates chemistry lab duration. In the middle of 1982 the price of copper shot up so the mint with help from the zinc. I drew the best fit line for my data, and drew the best fit line for the points. This lab cannot yield any evidence to support any particular answer to why the mass. In a modern physics textbook, the mass of a penny was used as part of a word problem. Instruct the students to determine the percent composition of the creme filling in a regular oreo. The zinc can be removed from the penny by cutting the coin and creating a reaction between. Step by step solution to find % cu in a penny when you know the total weight of coin and the molar amount of copper. The experiment will be using hcl a strong acid to dissolve all the zinc inside the outer copper shell.
Through the use of percent composition one can easily find out how much of a certain element is in a compound or an item such as a post1983 penny. Then, lets say you want to find the percent composition of the mg, you would take the molar mass of mg alone, divided by the total molar mass of compound. Ok so, we did a lab in chemistry, and i wasnt there for the experiment. Current model of the lincoln cent has the union shield on the reverse tail. Materials for mass percent of carbon in sodium bicarbonate are available from flinn scientific, inc. Calculate the atomic mass for the pennies as if they were an element. In the students experiment, the mass of a sample of molybdenum sulfide.
The purpose of this experiment is to determine the percent composition of carbon in a sample of sodium bicarbonate, nahco 3. If zinc completely reacts with hcl, then the theoretical yield of copper should be equivalent to the actual yield. One of the pennies was pre1982 while the other was post 1982. I will assume you can do this, as i am not going to waste my time doing it for you. If you are studying a chemical compound, you may want to find the percent composition of a certain element within that chemical compound. The mass of the copper formed was to be determined and the percentage yield was to be calculated. A lot of you did your best on the penny lab conclusion, but your best efforts were not quite aligned with what is best practice. Pennies are often mistakenly thought to be made of solid copper. Chemistry midterm all lab purpose and errors flashcards quizlet. We will determine the mass and volume of pennies minted prior to 1982 and pennies minted after 1982, separately and compare their densities. Penny lab report ib chemistry experiment 4 composition of a post1983 penny lab report background. In your lab notebook, solve equation 2 for the percent cu p.
This can be solved by cutting the penny directly in half. A chemical compound is the combination of two or more elements. Chem lab 12 maribel pacheco chem 140531430 experiment 5. Percent composition of zinc and copper in us pennies. It is known that naturally occurring boron is composed of two isotopes, boron10 and boron11. Percent composition penny lab free download as pdf file.
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