2. Consider the element Uranium, U. Determine which isotopes are naturally occurring. Look up the masses of each isotope in amu, and the natural abundances. Calculate the average atomic weight, and compare this to what you find in the periodic table. Given the atomic mass numbers of the isotopes, is the atomic mass number consistent with these atomic mass numbers? Why or why not? If it seems inconsistent, can you explain this apparent inconsistency?

2. Consider the element Uranium, U. Determine which isotopes are naturally occurring. Look up the masses of each isotope in amu, and the natural abundances. Calculate the average atomic weight, and compare this to what you find in the periodic table. Given the atomic mass numbers of the isotopes, is the atomic mass number consistent with these atomic mass numbers? Why or why not? If it seems inconsistent, can you explain this apparent inconsistency?

Chemistry: The Molecular Science

5th Edition

ISBN:9781285199047

Author:John W. Moore, Conrad L. Stanitski

Publisher:John W. Moore, Conrad L. Stanitski

Chapter2: Chemical Compounds

Section: Chapter Questions

Problem 29QRT: Argon has three naturally occurring isotopes: 0.3336% 36Ar, 0.063% 38Ar, and 99.60% 40Ar. Estimate...

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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 1.00g Oxygen Assumed Formula Hydrogen 0.126 g HO Sodium 2.875 g NaO Magnesium 1.500 g MgO How do your values compare with those in the periodic table? How do you account for any differences?
These questions concern the work of J. J. Thomson. a. From Thomsons work, which particles do you think he would feel are most important for the formation of compounds (chemical changes) and why? b. Of the remaining two subatomic particles, which do you place second in importance for forming compounds and why? c. Propose three models that explain Thomsons findings and evaluate them. To be complete you should include Thomsons findings.
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.
Chlorine has two isotopes, Cl-35 and Cl-37. Their abundances are 75.53% and 24.47%, respectively. Assume that the only hydrogen isotope present is H-1. (a) How many different HCI molecules are possible? (b) What is the sum of the mass numbers of the two atoms in each molecule? (c) Sketch the mass spectrum for HCI if all the positive ions are obtained by removing a single electron from an HCI molecule.
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.
The element europium exists in nature as two isotopes: 151Eu has a mass of 150.9196 u and 153Eu has a mass of 152.9209 u. The average atomic mass of europium is 151.96 u. Calculate the relative abundance of the two europium isotopes.
A gaseous binary compound has a vapor density that is 1.94 times that of oxygen at the same temperature and pressure. When 1.39 g of the gas is burned in an excess of oxygen, 1.21 g water is formed, removing all the hydrogen originally present. (a) Estimate the molecular mass of the gaseous compound. (b) How many hydrogen atoms are there in a molecule of the compound? (c) What is the maximum possible value of the atomic mass of the second element in the compound? (d) Are other values possible for the atomic mass of the second element? Use a table of atomic masses to identify the element that best fits the data. (e) What is the molecular formula of the compound?
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
There are 1.699 1022 atoms in 1.000 g of chlorine. Assume that chlorine atoms are spheres of radius 0.99 and that they are lined up side by side in a 0.5-g sample. How many miles in length is the line of chlorine atoms in the sample?
A cube of sodium has length 1.25 in. How many atoms are in that cube? (Note: dNa=0.968g/cm3.)
A mass spectrometer determines isotopic masses to eight or nine significant digits. What limits the atomic mass of carbon to only five significant digits?