14_440_407_Practice_Test_Spring_2010

14_440_407_Practice_Test_Spring_2010 - Practice...

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Practice Test (14-440:407) 1. (a) Describe the main characteristics of primary bonds in crystalline solids. (b) What type of bonding exists in the following: zinc oxide, tungsten, methane, solid argon? (c) Write down the chemical formula for a silicate tetrahedron and the corresponding sheet structure. 2. (a) Explain the following: ionization energy, electron affinity, coordination number, critical radius ratio. (b) Calculate the critical radius ratio for an ionic crystal with coordination number = 6. (c) Sketch the structures of the three known polymorphs of carbon. What are carbon nanotubes and why are they important? 3. The interaction energy between two point charges Q 1 and Q 2 , separated by distance r, is given by: E Q Q r b r n = + 1 2 0 4 πε (a) Derive an expression for the bond energy E b in terms of the bond distance r*. (b) For a divalent ionic solid, write down the expression for the cohesive energy/mole. (c) What information can be gained from the curvature and depth of the bond energy curve?
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