Ch 8
Supplemental Instruction
Iowa State University
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Leader:
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Grant DeRocher
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Course:
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Chem 167
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Instructor:
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Houk
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Date:
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03/05/13
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Do a problem from end of ch 7 first as review. Then 8.10, 8.13, 8.17, 8.19,
Next Exam is Wed March 13
2 hour Exam Review on Sunday March 10, Room TBD
4. Polonium is the only metal that forms a simple cubic crystal structure. Use the fact that the density of polonium is 9.32g/cm3 to calculate its atomic radius.
In the simple cubic crystal structure there are four Po atoms at the corners of each unit cell. The lengths of a unit cell, a, equals two times its radius, a=2r. The number of Po atoms resent in the simple cubic unit cell is 8*(1/8)=1 Po atom. The mass of one Po atoms is :. The volume of a unit cell is Vcell=(a)3
Using density we can solve for the volume in terms of the cell edge length, a, and then finally find a.
d=m/v; .
So cm.
Now the cell edge a=2r so r=a/2 = 3.34x10-8/2= 1.67x10-8 cm
5. Europium forms a body-centered cubic unit cell and has density of 4.68g/cm3. From this information, determine the length of the edge of a cubic cell.
The body centered cubic unit cell contains 8*(1/8) +1= 2 Eu atoms.
The mass of these two atoms is:
The volume of this unit cell is Vcell= (a)3
Using density, we can solve for volume in terms of the cell edge length, a, and then finally find a. d= m/V
So
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