UT CH 301 - Practice Exam 2 Key (8 pages)

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Practice Exam 2 Key



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Practice Exam 2 Key

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Lecture Notes


Pages:
8
School:
University of Texas at Austin
Course:
Ch 301 - Principles of Chemistry I
Principles of Chemistry I Documents

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CH301 Fall 2008 Practice Exam 2 Key 1 Which of the following statements are true I Bond polarity can be calculated using the differences in electronegativity values II Bond polarity describes to what degree electrons are shared between two atoms i e Is one atom hogging the electrons and how much III Homonuclear bonds are always polar IV F Br is a more polar bond than F I V Li B is less polar than O H VI O O is more polar than H H 1 I II and VI 2 I only 3 I and II 4 I II V correct 5 II V VI 6 II IV V 7 II and V Explanation I is true you will need to be able to do these calculations on the test because they will allow you to rank the polarities of various bonds II is true and describes bond polarity conceptually III is false because homonuclear bonds bonds between two atoms of the same element i e H H or O O are always NON POLAR because the difference in EN is always zero IV is false because the EN difference between F and I is larger than the EN difference between F and Br implying a more polar bond We know this because EN decreases down the periodic table V is true You must have memorized the EN values of all elements in the second row of the periodic table You will need them on the test In this case we see Li B has a difference in EN of 1 2 while O H has an EN difference of 1 3 Remember than a larger EN difference is a more polar bond VI is false These are both homonuclear bonds with an EN difference of ZERO meaning both bonds are completely nonpolar 2 Which of the following molecules is non polar 1 CO2 correct 2 H2O 3 CH3F O3 4 5 NO Explanation The only symmetrical molecules is carbon dioxide and it therefore cannot possibly be polar You might be tempted to pick ozone O3 because it has nonpolar bonds but if you draw the lewis structure you ll see that resonance puts a partial negative charge on the peripheral oxygens and that the structure is angular see Worksheet 4 2007 so the molecule ends up being polar 3 Which of the following statements are correct I If a



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