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Ch.6 - Electronic Structure of Atoms
All textbooksBrown 14th EditionCh.6 - Electronic Structure of AtomsProblem 107e
Chapter 6, Problem 107e

The discovery of hafnium, element number 72, provided a controversial episode in chemistry. G. Urbain, a French chemist, claimed in 1911 to have isolated an element number 72 from a sample of rare earth (elements 58–71) compounds. However, Niels Bohr believed that hafnium was more likely to be found along with zirconium than with the rare earths. D. Coster and G. von Hevesy, working in Bohr’s laboratory in Copenhagen, showed in 1922 that element 72 was present in a sample of Norwegian zircon, an ore of zirconium. (The name hafnium comes from the Latin name for Copenhagen, Hafnia). (c) Solid zirconium dioxide, ZrO2, reacts with chlorine gas in the presence of carbon. Starting with a 55.4-g sample of ZrO2, calculate the mass of ZrCl4 formed, assuming that ZrO2 is the limiting reagent and assuming 100% yield.

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1
Write the balanced chemical equation for the reaction: ZrO2 + 2Cl2 + 2C -> ZrCl4 + 2CO.
Calculate the molar mass of ZrO2 by adding the atomic masses of zirconium (Zr) and oxygen (O).
Determine the number of moles of ZrO2 in the 55.4 g sample by dividing the mass of ZrO2 by its molar mass.
Using the stoichiometry of the balanced equation, find the number of moles of ZrCl4 produced from the moles of ZrO2, noting that the molar ratio of ZrO2 to ZrCl4 is 1:1.
Calculate the mass of ZrCl4 formed by multiplying the number of moles of ZrCl4 by its molar mass, which is the sum of the atomic masses of zirconium (Zr) and chlorine (Cl).

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Related Practice
Open Question
The stratospheric ozone (O3) layer helps to protect us from harmful ultraviolet radiation. It does so by absorbing ultraviolet light and falling apart into an O2 molecule and an oxygen atom, a process known as photodissociation. O3(g) → O2(g) + O(g). Use the data in Appendix C to calculate the enthalpy change for this reaction. What is the maximum wavelength a photon can have if it is to possess sufficient energy to cause this dissociation? In what portion of the spectrum does this wavelength occur?
Textbook Question

The discovery of hafnium, element number 72, provided a controversial episode in chemistry. G. Urbain, a French chemist, claimed in 1911 to have isolated an element number 72 from a sample of rare earth (elements 58–71) compounds. However, Niels Bohr believed that hafnium was more likely to be found along with zirconium than with the rare earths. D. Coster and G. von Hevesy, working in Bohr's laboratory in Copenhagen, showed in 1922 that element 72 was present in a sample of Norwegian zircon, an ore of zirconium. (The name hafnium comes from the Latin name for Copenhagen, Hafnia). (a) How would you use electron configuration arguments to justify Bohr's prediction?

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Textbook Question

The discovery of hafnium, element number 72, provided a controversial episode in chemistry. G. Urbain, a French chemist, claimed in 1911 to have isolated an element number 72 from a sample of rare earth (elements 58–71) compounds. However, Niels Bohr believed that hafnium was more likely to be found along with zirconium than with the rare earths. D. Coster and G. von Hevesy, working in Bohr's laboratory in Copenhagen, showed in 1922 that element 72 was present in a sample of Norwegian zircon, an ore of zirconium. (The name hafnium comes from the Latin name for Copenhagen, Hafnia). (d) Using their electron configurations, account for the fact that Zr and Hf form chlorides MCl4 and oxides MO2.

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Open Question
(c) Consider the metal oxides whose enthalpies of formation (in kJ mol⁻¹) are listed here: Oxide K₂O₍s₂₎, CaO₍s₂₎, TiO₂₍s₂₎, V₂O₅₍s₂₎, ΔHf° -363.2, -635.1, -938.7, -1550.6. Calculate the enthalpy changes in the following general reaction for each case: MnOm₍s₂₎ + H₂(g) → nM₍s₂₎ + mH₂O(g). (You will need to write the balanced equation for each case and then compute ΔH°.)
Textbook Question

The first 25 years of the twentieth century were momentous for the rapid pace of change in scientists' understanding of the nature of matter. (b) In what ways is de Broglie's hypothesis, as it applies to electrons, consistent with J. J. Thomson's conclusion that the electron has mass? In what sense is it consistent with proposals preceding Thomson's work that the cathode rays are a wave phenomenon?

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Textbook Question

The two most common isotopes of uranium are 235U and 238U. (b) Using the periodic table in the frontinside cover, write the electron configuration for a U atom.

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