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Test1-soln

# Test1-soln - Name Team 1 ENGR 213 Test#1a 25 SEP 02 Attempt...

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Name_______________________________ Team#_________ 1 ENGR 213 Test #1a 25 SEP 02 Attempt all problems. SOLUTION 1. Define bonding energy and give characteristic ranges for the three types of primary bond. The energy required to separate (to infinity) two bonded atoms. 4 points Ionic: 600 – 1500 kJ/mol or 3 -- 8 eV/atom 2 pts each answer Covalent: 70 – 700 kJ/mol or 0.7 – 7 eV/atom Metallic: 70 – 850 kJ/mol or 0.7 – 9 eV/atom 2. Describe how bonding energy affects the melting point of a material. Larger bonding energies require higher temperatures 8 pts Because bonds must be broken for melting to occur 2 pts 3. Calculate the APF for a BCC crystal structure. APF = (volume of ions or atoms in unit cell) / (volume of unit cell) 4 pts For BCC crystal, there are two atoms per cell 1 pts Volume of ions in cell = 2(4 π R 3 /3) = 8 π R 3 /3 1 pt Volume of cell = (4R/ 3) 3 1 pt APF = (3 3)(8 π R 3 )/(3x64R 3 ) = 3 π /8 = 0.68 3 pt 4. Calculate the theoretical density of fluorite CaF 2 , whose unit cell is shown at right.

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Test1-soln - Name Team 1 ENGR 213 Test#1a 25 SEP 02 Attempt...

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