# prelab 8

Good Essays
564 Words
Grammar
Plagiarism
Writing
Score
prelab 8
DETERMINATION OF % COMPOSITION OF PENNIES USING REDOX AND DOUBLE DISPLACEMENT (PRECIPITATION) REACTIONS
Pre- Lab 8
Objective: The purpose of this experiment is to determine the percent composition of pennies using oxidation-reduction and double displacement reactions as well as titration techniques. We will take a post 1982 penny and place in a strong acid dissolving the zinc core and leaving behind the copper coating. We will figure out the percent composition from the mass of copper and zinc using titration and precipitation.
Procedure:
1) First dissolve the zinc core of a penny and leave copper covering intact by applying four notches in the coin using a triangular file.
2) Place the penny in a 50 mL of a pre-determined concentration of HCl solution overnight.
3) Then determine the percent copper from the mass of copper.
4) Find the percent of zinc by precipitation and titration
5) If there is a known amount of HCl added to the beaker that penny is placed in, then determine the amount of HCl that was used up in the reaction of HCl and Zinc. Calculate the % of zinc in penny.
6) If zinc reacts with NaOH in the titration experiment, then zinc hydroxide will form. Check solubility rules to see if zinc hydroxide is soluble of insoluble. Then calculate for % zinc in penny.

Questions:
1. What is the weight of a post 1982 penny? 2.5 grams
2. What is the percent copper and zinc in a post 1982 penny? 97.5% Zn and 2.5% Cu
3. How many grams of copper and zinc are in a post 1982 penny?
(2.5)(.025)= 0.0625 grams of Copper and (2.5)(.975)= 2.4375 grams of Zinc

4. How many moles of copper and zinc are in post 1982 pennies?

5. Write a balanced reaction of zinc with HCl. Zn (s) + 2HCl (aq)  ZnCl2 (aq) +H2 (g)
6. How many moles of HCl are needed to react completely with all of the zinc in a post 1982 penny?

7. In a procedure developed to determine the percent zinc in post 1982 pennies, 50 ml of an HCl solution was used to react (dissolve) all of the zinc in

## You May Also Find These Documents Helpful

• Good Essays

zinc and the hydrochloric acid combined to create zinc chloride. You know the mass of zinc used, and the mass of zinc chloride…

• 1376 Words
• 6 Pages
Good Essays
• Satisfactory Essays

b) 1.67 x 10-2 moles x 6.02x1023 molecule x 1 atom = 1.01 x 1022 atoms of copper produced…

• 440 Words
• 2 Pages
Satisfactory Essays
• Good Essays

In table 1.2, the mixture of HCl and unkown sample 2 were combined. It took 40mL of HCl to turn the solution yellow, after the heating and evaporation of the water, the glassware with the NaCl weighed 76.38g. When the glassware was weighed again after the NaCl was washed out, it was 76.24g. There was 0.14g of NaCl that had formed.…

• 420 Words
• 2 Pages
Good Essays
• Good Essays

Step 5 repeat steps 1-4 using pH meter, add a pH meter to the acid solution. Record numerous points of pH and NaOH added (especially near equivalence point) to be used later to prepare a titration curve.…

• 496 Words
• 2 Pages
Good Essays
• Good Essays

In this lab, we will determine the percent composition of a modern (post-1982) penny by using a strong acid to react and dissolve the zinc core, leaving only the copper coating. Once only copper remains, we will compare its mass to the entire mass of the penny to determine how much of a penny is copper and how much is zinc.…

• 623 Words
• 3 Pages
Good Essays
• Good Essays

Before 1982 the US penny was made of pure copper. Because of the high cost of copper, the US government changed the composition of the penny. As of 1982, pennies have been made of mostly zinc, with a thin copper layer on the outside. The first step in finding the % of copper is to make solution out of the penny. In other words “liquefy” the penny. To differentiate between the copper and zinc; zinc is clear and copper turns blue. During this lab, we will be making several standard solutions of this penny solution. To find out each solutions concentration, we will find its molarity by using the formula:…

• 916 Words
• 5 Pages
Good Essays
• Satisfactory Essays

In the Penny Cleaning Lab, my hypothesis, which stated that the lemon juice would be the best at cleaning the penny since it is an acid and acids are particularly good at cleaning metallic substances, was indeed valid. First, we started out with 1mL solutions of all the substances in the test tray. We dipped the pH paper in each solution for about a second and recorded the pH level for each substance. Before starting, we noticed that all the pennies were in some shade of brown, which I predicted this to be copper oxide. In order to make things as efficient as possible, we soaked two pennies at a time for three minutes for each solution and penny. After taking out the first two pennies, which were soaked in liquified Bon Ami and Tapatio Hot…

• 400 Words
• 2 Pages
Satisfactory Essays
• Good Essays

The goal of this lab is to find out which metals were used in the minting of pennies before and after 1982 by calculating their densities.…

• 358 Words
• 2 Pages
Good Essays
• Powerful Essays

6. How many moles of HCl are needed to react completely with all of the zinc in a post 1982 penny?…

• 754 Words
• 3 Pages
Powerful Essays
• Satisfactory Essays

The purpose of this lab is to create an experiment where zinc reacts with hydrochloric acid in order to find out the number of moles and atoms of zinc reacted. This can be accomplished by weighing the sample before and after the reaction with hydrochloric acid.…

• 440 Words
• 2 Pages
Satisfactory Essays
• Good Essays

In this lab, each person in the group will have two pennies. Galvanization of a penny will create a brass penny. Galvanizing the penny in sodium hydroxide with zinc causes the penny to turn from bronze to silver. Once the penny is fully galvanized you will burn the penny and spray it off and then it will turn gold. There will be a weight change also a mass change. Observing the penny to see it turn from bronze to silver to gold.…

• 560 Words
• 3 Pages
Good Essays
• Good Essays

Introduction. The purpose of this experiment was to find a sufficient price to charge for galvanizing nails. In order to do this the mass of zinc coating on a typical galvanized nail needs to be known. Two different methods were used to obtain these values. Gravimetric analysis was used by measuring the mass of the nail with the zinc coating and then subtracting the mass of the nail after the zinc was dissolved in acid. Gasometric analysis was used by measuring the total hydrogen yield of the reaction. Stoichiometry was then used to find a molar ratio between hydrogen and zinc. After calculating the moles of zinc, the mass can then be figured by multiplying by the molar mass of zinc.…

• 642 Words
• 3 Pages
Good Essays
• Good Essays

3- One by one add the drops of water to the top of the penny…

• 659 Words
• 3 Pages
Good Essays
• Satisfactory Essays

1. Write a balanced equation for each reaction observed in this lab. (10 points total, 2 points each)…

• 340 Words
• 2 Pages
Satisfactory Essays
• Good Essays

While the experiment was taking place, I was comparing the amount of the zinc chloride…

• 383 Words
• 2 Pages
Good Essays