An unknown element (Uk) has three isotopes, seen in the table. One of the percentage values is missing. Percent Abundance Isotope Notation Mass (amu) (%) Uk-66 65.994 56.00 Uk-69 68.958 14.00 Uk-71 70.975 Once you have found the missing percentage, calculate the average atomic mass of Uk. Enter your answer to the hu

An unknown element (Uk) has three isotopes, seen in the table. One of the percentage values is missing. Percent Abundance Isotope Notation Mass (amu) (%) Uk-66 65.994 56.00 Uk-69 68.958 14.00 Uk-71 70.975 Once you have found the missing percentage, calculate the average atomic mass of Uk. Enter your answer to the hu

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 43E: The element europium exists in nature as two isotopes: 151Eu has a mass of 150.9196 u and 153Eu has...

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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.
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.
A sample of ammonia, NH3, contains 1.2 1023 hydrogen atoms. How many NH3 molecules are in this sample?
A cube of sodium has length 1.25 in. How many atoms are in that cube? (Note: dNa=0.968g/cm3.)
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.
These questions concern the work of J. J. Thomson: From Thomson’s work, which particles do you think he would feel are most important in the formation of compounds (chemical changes) and why? Of the remaining two subatomic particles, which do you place second in importance for forming compounds and why? Come up with three models that explain Thomson’s findings and evaluate them. To be complete you should include Thomson’s findings.
he chemical formula for aspirin is C9H8O4 . What is the mass percent for each element in 1 mole of aspirin? (Give your answer to four significant figures.) l type="a"> carbon > % l type="a"> hydrogen > % l type="a"> oxygen > %
Consider the chemical reaction as depicted below. Label as much as you can using the terms atom, molecule, element, compound, ionic, gas, and solid.
A mass spectrometer determines isotopic masses to eight or nine significant digits. What limits the atomic mass of carbon to only five significant digits?
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=0.968 g/cm3.)
The following chart shows a general decline in abundance with increasing mass among the first 30 elements. The decline continues beyond zinc. Notice that the scale on the vertical axis is logarithmic, that is, it progresses in powers of 10. The abundance of nitrogen, for example, is 1/10,000 (1/104) of the abundance of hydrogen. All abundances are plotted as the number of atoms per 102 atoms of H. (The fact that the abundances of Li, Be, and B, as well as those of the elements near Fe, do not follow the general decline is a consequence of the way that elements are synthesized in stars.) (a) What is the most abundant main group metal? (b) What is the most abundant nonmetal? (c) What is the most abundant metalloid? (d) Which of the transition elements is most abundant? (e) Which halogens are included on this plot, and which is the most abundant?