exam2.studyguide.2011

exam2.studyguide.2011 - CHE131 Fall 2011 exam#2 study guide...

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10/13/2011 Fall 2010 CHE131 Exam #2 study guide by Prof. Carlos Simmerling 1 © 2011 Carlos Simmerling CHE131 Fall 2011 exam #2 study guide Prof. Carlos Simmerling This study guide is just a summary. Although I attempted to make it comprehensive, there may be information needed for the exam that is not covered here. There is no substitute for working practice problems and reading your notes. 2 © 2011 Carlos Simmerling Exam #2 • 26 multiple choice problems • Some conceptual, some numerical • A few have multiple steps and take time • Point value same regardless of difficulty! • Budget your time carefully • Review lecture notes • PRACTICE problem solving • Do not work too hard monday PM Do not attempt “new” material 24 hours before exam

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10/13/2011 Fall 2010 CHE131 Exam #2 study guide by Prof. Carlos Simmerling 5 © 2011 Carlos Simmerling General Units and molecular formulas 6 © 2011 Carlos Simmerling Weighted averages • Consider 8 coins in your pocket. 3 nickels and 5 dimes • What is the average value in cents? (5+5+5+10+10+10+10+10)cents / 8 coins- = 3/8 * 5 cents/coin + 5/8 * 10 cents/coin = 8.125 cents/coin - Average is the value of each type times the fraction of coins with that value - Works the same way for average mass of isotope mixtures

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10/13/2011 Fall 2010 CHE131 Exam #2 study guide by Prof. Carlos Simmerling 7 © 2011 Carlos Simmerling Dimensional Analysis; unit conversion • Most numbers have associated UNITS • Salary=16. Is that dollars/hour, or thousands of dollars per year?? Or pesos/yen/pennies??? • Units can help you SOLVE PROBLEMS. 1. What are the units of the unknown? 2. What are the units of the knowns? 3. What type of equation or conversion do I need to get from 1 to 2? 8 © 2011 Carlos Simmerling Example of dimensional analysis • What mass of C is in 1.502g CO 2 ? 1.502 g CO 2 = 0.4099 g C 1 mol CO 2 44.009 g CO 2 12.011 g C 1 mol C 1 mol C 1 mol CO 2
10/13/2011 Fall 2010 CHE131 Exam #2 study guide by Prof. Carlos Simmerling 9 © 2011 Carlos Simmerling Conversions • Converting between a number of particles and an equivalent number of moles (or vice versa) is a matter of dividing (or multiplying) by Avogadro’s number.

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exam2.studyguide.2011 - CHE131 Fall 2011 exam#2 study guide...

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