MTLS 1M03 Assignment 2 Attempt4

# MTLS 1M03 Assignment 2 Attempt4 - Learning System Quiz...

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View Results Assignment 2 (Ch 4 & 5) Name: SIAMAK KIANI Attempt: 2 / 3 Out of: 18 Started: January 30, 2009 10:05pm Finished: February 3, 2009 12:46am Time spent: 74 hr, 41 min., 2 sec. Question 1 (1 point) True or false? In metals, there are significantly more vacancies than self-interstitials. Student response: Percent Value Correct Response Student Response Answer Choices 100.0% a. True 0.0% b. False General feedback: True . In metals, there are significantly more vacancies than self-interstitials. Score: 0 / 1 Question 2 (1 point) True of False: The introduction of impurity atoms into a highly pure metal is never desirable. The properties of the metal are always adversely affected. Student response: Correct Response Student Response Answer Choices a. True b. False General feedback: Introducing impurity atoms into an originally highly pure substance can sometimes improve material properties. Carbon is added to iron to make steel. Alloys are solid solutions of more than one metal, combined intentionally to give the material specific desirable properties. Score: 1 / 1 Question 3 (1 point) The number of vacancies present in some metal at 907°C is 6.55 x 10 24 m -3 . Calculate the number of vacancies at 572°C (in m^-3) given that the energy for vacancy formation is 0.570 eV/atom. Assume that the density of the metal remains constant. Use scientific notation, significant figures in answer: 3 Student response: 7.11e23 m^-3 Correct answer: 7.10E23 (7.10 * 10 23 ) m^-3 General feedback: See section 4.2 in the text. Score: 1 / 1 Question 4 (1 point) For a Pb-Sn alloy that consists of 11.81 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: 92.87 at% Learning System Quiz Homepage http://webct.mcmaster.ca/SCRIPT/MATLS_1M03_T2_09/scripts/student/... 1 of 4 2/3/2009 1:02 AM

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Correct answer: 92.87 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.
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