5. Boron exists as two isotopes, Boron-10 and Boron-11. The average atomic mass for boron on found on a periodic table is 10.81 amu. Estimate the relative abundance of Boron-11 found in nature. If you are not sure, go to the simulation. Hint: Check you answer against the simulation for boron. 100% 80% 20% 50%

5. Boron exists as two isotopes, Boron-10 and Boron-11. The average atomic mass for boron on found on a periodic table is 10.81 amu. Estimate the relative abundance of Boron-11 found in nature. If you are not sure, go to the simulation. Hint: Check you answer against the simulation for boron. 100% 80% 20% 50%

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter3: Stoichiometry

Section: Chapter Questions

Problem 25Q: The atomic masses in die periodic table are relative masses and average masses. Explain.

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Average atomic masses listed by JUPAC are based on a study of experimental results. Bromine has two isotopes 79Br and 81Br, whose masses (78.9 183 and 80.9 163 amu) and abundances (50.69% and 49.3 1%) were determined in earlier experiments. Calculate the average atomic mass of bromine based on these experiments.
Click on the site (http://openstaxcollege.org/l/16PhetAtomMass) and select the Mix Isotopes tab, hide the Percent Composition and Average Atomic Mass boxes, and then select the element boron. Write the symbols of the isotopes of boron that are shown as naturally occurring in significant amounts. Predict the relative amounts (percentages) of these boron isotopes found in nature. Explain the reasoning behind your choice. Add isotopes to the black box to make a mixture that matches your prediction in (b). You may drag isotopes from their bins or click on More and then move the sliders to the appropriate amounts. Reveal the Percent Composition and Average Atomic Mass boxes. How well does your mixture match with your prediction? If necessary, adjust the isotope amounts to match your prediction. Select Nature’s mix of isotopes and compare it to your prediction. How well does your prediction compare with the naturally occurring mixture? Explain. If necessary, adjust your amounts to make them match Nature’s amounts as closely as possible. 21. Repeat Exercise 2.20 using an element that has three naturally occurring isotopes.
Average Atomic Weight Part 1: Consider the four identical spheres below, each with a mass of 2.00 g. Calculate the average mass of a sphere in this sample. Part 2: Now consider a sample that consists of four spheres, each with a different mass: blue mass is 2.00 g, red mass is 1.75 g, green mass is 3.00 g, and yellow mass is 1.25 g. a Calculate the average mass of a sphere in this sample. b How does the average mass for a sphere in this sample compare with the average mass of the sample that consisted just of the blue spheres? How can such different samples have their averages turn out the way they did? Part 3: Consider two jars. One jar contains 100 blue spheres, and the other jar contains 25 each of red, blue, green, and yellow colors mixed together. a If you were to remove 50 blue spheres from the jar containing just the blue spheres, what would be the total mass of spheres left in the jar? (Note that the masses of the spheres are given in Part 2.) b If you were to remove 50 spheres from the jar containing the mixture (assume you get a representative distribution of colors), what would be the total mass of spheres left in the jar? c In the case of the mixture of spheres, does the average mass of the spheres necessarily represent the mass of an individual sphere in the sample? d If you had 80.0 grams of spheres from the blue sample, how many spheres would you have? e If you had 60.0 grams of spheres from the mixed-color sample, how many spheres would you have? What assumption did you make about your sample when performing this calculation? Part 4: Consider a sample that consists of three green spheres and one blue sphere. The green mass is 3.00 g, and the blue mass is 1.00 g. a Calculate the fractional abundance of each sphere in the sample. b Use the fractional abundance to calculate the average mass of the spheres in this sample. c How are the ideas developed in this Concept Exploration related to the atomic weights of the elements?
Match these by placing the correct notation in the appropriate blank. 3467Se3367As3567Br3672Kr a. Contains 33 neutrons b. Contains greatest number of neutrons c. Contains equal number of protons and neutrons d. Contains the same number of neutrons as there are protons in As-67
Click on the site (http://openstaxcollege.org/l/16PhetAtomMass) and select the Mix Isotopes tab, hide the Percent Composition and Average Atomic Mass boxes, and then select the element boron. Write the symbols of the isotopes of boron that are shown as naturally occurring in significant amounts. Predict the relative amounts (percentages) of these boron isotopes found in nature. Explain the reasoning behind your choice. Add isotopes to the black box to make a mixture that matches your prediction in (b). You may drag isotopes from their bins or click on More and then move the sliders to the appropriate amounts. Reveal the Percent Composition and Average Atomic Mass boxes. How well does your mixture match with your prediction? If necessary, adjust the isotope amounts to match your prediction. Select Nature’s mix of isotopes and compare it to your prediction. How well does your prediction compare with the naturally occurring mixture? Explain. If necessary, adjust your amounts to make them match Nature’s amounts as closely as possible.
The average atomic masses of some elements may vary, depending upon the sources of their ores. Naturally occurring boron consists of two isotopes with accurately known masses ( 10B, 10.0129 amu and 11B, 11.0931 amu). The actual atomic mass of boron can vary from 10.807 to 10.8 19, depending on whether the mineral source is from Turkey or the United States. Calculate the percent abundances leading to the two values of the average atomic masses of boron from these two countries.
Argon has three naturally occurring isotopes: 0.3336% 36Ar, 0.063% 38Ar, and 99.60% 40Ar. Estimate the average atomic mass of argon. If the masses of the isotopes are 35.968 u, 37.963 u, and 39.962 u, respectively, calculate the average atomic mass of natural argon.
An isotope of an element contains 63 protons and 91 neutrons. (a) Identify the element and give its symbol. (b) Give the elements atomic number. (c) Give the mass number of the isotope. (d) This element has two naturally occurring isotopes. Given the information in the table, calculate the atomic weight of the element. (e) In which region of the periodic table is the element found? Explain your answer. (f) Is the element a metal, metalloid, or nonmetal? Explain your answer. (g) This element, used in compact fluorescent light bulbs and computer screens, has an atomic radius of 180 pm. Calculate how long the chain of atoms would be if all the atoms in a 1.25-mg sample of this element were put into a row.
Uranium-235 is the isotope of uranium commonly used in nuclear power plants. How many (a) protons are in its nucleus? (b) neutrons are in its nucleus? (c) electrons are in a uranium atom?
The atomic masses in die periodic table are relative masses and average masses. Explain.
Early tables of atomic weights (masses) were generated by measuring the mass of a substance that reacts with 1.00 g of oxygen. Given the following data and taking the atomic mass of hydrogen as 1.00, generate a table of relative atomic masses for oxygen, sodium, and magnesium. Element Mass That Combines with 1.00Oxygen Assumed Formula Hydrogen 0.126g HO Sodium 2.875g Nao Magnesium 1.500g Mgo
Gather any two of the following items, measure their dimensions, and calculate the number of atoms present in the item. a. a copper penny (pre-1983), density of copper = 8.96g/cm3 b. a nickel (assume that the nickel is pure nickel, Ni), density of nickel = 8.90g/cm3 c. a graphite pencil lead (pure carbon), density of carbon = 2.62g/cm3 d. a helium balloon (assume that the balloon is approximately spherical; the volume of a sphere is V=(43)r3, where r is the radius), density of helium gas = 0.0899 g/L