1M03 2009 ASSIGNMENT 2-1 ¿¯

1M03 2009 ASSIGNMENT 2-1...

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Name: SOO NAM Attempt: 1 / 3 Out of: 18 Started: January 29, 2009 5:46am Finished: February 2, 2009 8:19pm Time spent: 110 hr, 33 min., 5 sec. Question 1 (1 point) What is the maximum purity (in at%) that can be practically achieved in metals? Student response: Correct Response Student Response Answer Choices a. 72% b. 88% c. 97% d. 99.1% e. 99.9999% General feedback: See page 68 of the text book for more details. Score: 1 / 1 Question 2 (1 point) _________________ point defects occur when impurity atoms fill the voids or interstices between host atoms in the crystal structure. Student response: No. Student response Grade Correct answer (Value) 1. Interstitial 100% Answer evaluated by the formula. (100%) General feedback: Interstitial point defects involve impurity atoms filling the voids between atoms in the regular crystal lattice. See page 69 in the text. Score: 1 / 1 Question 3 (1 point) Calculate the energy for vacancy formation (in eV/atom) in a metal given that the equilibrium number of vacancies at 493°C is 4.60x10 24 per m 3 . The density and atomic weight for this metal are 13.5 g/cm 3 and 174 g/mol, respectively. Use decimal notation, digits after decimal: 3 Student response: 0.609 eV/atom Correct answer: 0.609 eV/atom General feedback: See pages 67-68 of the text for a similar example. Score: 1 / 1 Question 4 (1 point) For a Pb-Sn alloy that consists of 51.27 wt% Pb, what is the composition of Sn (in at%)? The atomic weights for Pb and Sn are 207.2 and 118.7 g/mol, respectively. Use decimal notation, digits after decimal: 2 Student response: 62.39 % Correct answer: 62.39 at% General feedback: For help on composition conversions, please see page 71 of the textbook. An example similar to this question is given on page 73. Score:
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1M03 2009 ASSIGNMENT 2-1...

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