110_Fa11_LUZ-PracticeExamples_9_26 (1)

110_Fa11_LUZ-PracticeExamples_9_26 (1) - Answer: C Practice...

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Practice Example: A compound consists of sulfur and oxygen, and contains 40.0% S by mass. Assuming that its empirical formula is the same as its molecular formula, what is the molecular geometry of this compound? A. linear B. bent C. trigonal planar D. tetrahedral E. trigonal pyramidal Strategy: Assume 100 g sample, use mass percent to find grams of S and O, use molar mass of S and O to find moles of S and O, finally calculate S and O molar ratio to obtain empirical and molecular formula SO 3 . Draw Lewis structure of SO 3 to predict its electron domain geometry and molecular geometry.
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Unformatted text preview: Answer: C Practice Example: Which is the correct ordering of H-N-H bond angles (starting with the smallest) in NH 2 ! , NH 3 , and NH 4 + ? A. NH 4 + < NH 3 < NH 2 ! B. NH 3 < NH 4 + < NH 2 ! C. NH 3 < NH 2 ! < NH 4 + D. NH 2 ! < NH 4 + < NH 3 E. NH 2 ! < NH 3 < NH 4 + Solve: Draw Lewis structures of all three species. All three have 4 electron domains around N, NH 2 ! has 2 bonding pairs, 2 lone pairs, NH 3 has 3 bonding pairs, 1 lone pair, and NH 4 + has 4 bonding pairs, 0 lone pair. Bond angle decreases as the number of lone pairs increases, so answer is E ....
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This note was uploaded on 01/18/2012 for the course CHEM 110 taught by Professor Hofmann,brucerob during the Fall '08 term at Penn State.

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