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Concept explainers
On October 21, 1982, the Bureau of the Mint changed the composition of pennies (see Exercise 120). Instead of an alloy of 95% Cu and 5% Zn by mass, a core of 99.2% Zn and 0.8% Cu with a thin shell of copper was adopted. The overall composition of the new penny was 97.6% Zn and 2.4% Cu by mass. Does this account for the difference in mass among die pennies in Exercise 120? Assume the volume of the individual metals that make up each penny can be added together to give the overall volume of the penny, and assume each penny is the same size. (Density of Cu = 8.96 g/cm3; density of Zn = 7.14 g/cm3).
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Interpretation:
The density of the old and new pennies has to be calculated and the reason for the change in mass with change in alloy used has to be explained.
Concept introduction:
The quantity density the amount of substance per unit volume of the substance. Density is a unique property of a substance.
Answer to Problem 121CP
The density of the old penny is
The density of the new penny is
From the density measurements of the old and new pennies, we have found that there is a change in density along with the change in the composition. Hence, we can conclude that the change in mass is due the difference in the alloys that is used for the preparation of pennies.
Explanation of Solution
To find the density of the old penny
Given,
Density of one mole of copper
Density of one mole of zinc
Let's assume there are
The total volume is the sum of the volume of copper and zinc.
To find the density of the new penny
Given,
Density of one mole of copper
Density of one mole of zinc
Let's assume there are
The total volume is the sum of the volume of copper and zinc.
From the density measurements of the old and new pennies, we have found that there is a change in density along with the change in the composition. Hence, we can conclude that the change in mass is due the difference in the alloys that is used for the preparation of pennies.
The density of the old and new pennies has been calculated and the reason for the change in mass with change in alloy used has been explained.
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Chapter 1 Solutions
Chemistry
- 2. 200 LOD For an unknown compound with a molecular ion of 101 m/z: a. Use the molecular ion to propose at least two molecular formulas. (show your work) b. What is the DU for each of your possible formulas? (show your work) C. Solve the structure and assign each of the following spectra. 8 6 4 2 (ppm) 150 100 50 ō (ppm) 4000 3000 2000 1500 1000 500 HAVENUMBERI-11arrow_forwardComplete the spectroscopy with structurearrow_forwardComplete the spectroscopy with structurearrow_forward
- Given the following concentrations for a system, calculate the value for the reaction quotient: Cl2(g)+ CS2(g) ⇌ CCl4(g)+ S2Cl2(g) Cl2 = 31.1 atm CS2 = 91.2 atm CCl4 = 2.12 atm S2Cl2 = 10.4 atmarrow_forwardMatch each chemical or item with the proper disposal or cleanup mwthod, Not all disposal and cleanup methods will be labeled. Metal sheets C, calcium, choroide solutions part A, damp metal pieces Part B, volumetric flask part A. a.Return to correct lables”drying out breaker. Place used items in the drawer.: Rinse with deionized water, dry as best you can, return to instructor. Return used material to the instructor.: Pour down the sink with planty of running water.: f.Pour into aqueous waste container. g.Places used items in garbage.arrow_forwardWrite the equilibrium constant expression for the following reaction: HNO2(aq) + H2O(l) ⇌ H3O+(aq) + NO2-(aq)arrow_forward
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