IB strong acid to dissolve all the
IB Chemistry Experiment 4 Composition of a Post-1983 Penny Lab Report Background: 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 post-1983 penny. The experiment will be using HCl a strong acid to dissolve all the zinc inside the outer copper shell. The reaction follows as such; Zn+2HCLZnCl2+H2, but there will be no reaction with copper. The portion that will be measured is the mass of copper left after all of the Zn goes through the reaction process.
Hypothesis: If the penny is post-1983, then there will be a percent yield of copper greater than 30%. Research Question: What is the percent composition of Copper and Zinc in a post-1983 penny? Aim: The purpose is to determine the percent composition of Zinc and Copper metals in a post-1983 penny with the use of HCl. Variables: Independent Variable: percent composition of Zinc. Dependent Variable: percent composition of Copper. Controlled Variable: Molarity of HCl, and year of penny.
Apparatus:Beaker Penny Goggles HCl Filler Distilled Water Method: Note that HCl is an acid and must be cautious around this acid for it can burn your eyes so wear goggles, and wash hands after the lab. 1.Retrieve a penny that is post 1983, and clean and dry the beaker you are going to use to make sure it has no residue from any previous users. 2. Fill 3 slots into a copper about 1/3 of the way or till you see the gray portion.
(Note it will be more effective if each filling mark is at 120o angle of each other. ) 3. Once the penny has been filed, weigh it and record its mass. 4. Weight the beaker and record it’s mass, then add penny in the beaker and mass or you can indirectly measure the mass by adding the penny mass with the beaker mass. 5.
Place the penny in the beaker and add the HCl.Let sit for a day and recover your penny. 6. After the penny seems hollow retrieve the copper shell and mass it. 7. Once massed use the percent composition formula to find out how much copper is in a penny. (Percent composition formula: % comp= partial masstotal mass x 100) 8.
Subtract your finding of the percent composition of copper from 100 to find percent composition of zinc. 9. Repeat steps for multiple trials. Data: Date of Penny: 1984 Mass of Beaker: 29. 99g Mass of penny: 2.
62g Mass of beaker + penny: 32. 61 Mass of copper residue: . 91g % comp Copper: 35% . 91g2.
2g x 100 = 35% Cu % comp. Zn-65% 100%-35%= 65% Pre Mass (g)| Post Mass (g)| % composition Cu| % composition Zn| 2. 36g| 0. 50g| 21%| 79%| 2. 37g| 0.
72g| 30%| 70%| 2. 48g| 0. 73g| 29%| 71%| 2. 40g| 0.
45g| 19%| 81%| Average Mass of Copper= 21%+30%+29%+19%+35%5=26. 8% Avg. Cu Conclusion: At the end of the experiment, through the use of percent composition, the copper within the post-1983 penny was found to be 35 percent, and 65 percent zinc. Some sources of error were filing the penny’s sides to open it up for the reaction. The only solution to the problem is keep filing the.
Human error was the largest source of error in the lab. Finding the mass of two objects and using indirect measurements could lead you to the wrong number depending on rounding, thus slightly increasing or decreasing your percent yield in the experiment. Also if you use the wrong sig figs while solving for the percent composition this could cause problems. If I were to retry lab, I would make sure to file more than what I thought was needed, and to make sure to get a penny of the same year for a second trial.
By adding a catalyst, a change in the speed of the reaction could reduce the time needed.