exam 2 - Version 075 Exam 2 mccord (50970) This print-out...

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Version 075 – Exam 2 – mccord – (50970) 1 This print-out should have 34 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points Consider the Following pairs A and B A 1 ) N N O b b b b b b b b A 2 ) N N O b b b b b b b b B 1 ) P O O O O b b b b b b b b b b b b b b b b b b b b b b 3 B 2 ) P O O O O b b b b b b b b b b b b b b b b b b b b 3 oF Lewis structures. Select the one From each pair that is likely to make the dominant contribution to a reso- nance hybrid. 1. A 2 and B 1 correct 2. A 1 and B 1 3. A 1 and B 2 4. A 2 and B 2 Explanation: A 1 ) N N O b b b b b b b b - 1 +1 0 A 2 ) N N O b b b b b b b b 0 +1 - 1 The second structure is preFerred because it places the negative Formal charge on the most electronegative atom. B 1 ) P O O O O b b b b b b b b b b b b b b b b b b b b b b 0 - 1 - 1 - 1 0 3 B 2 ) P O O O O b b b b b b b b b b b b b b b b b b b b 0 0 - 1 - 1 - 1 3 The frst structure is preFerred For the same reason. 002 10.0 points Which is the most polar molecule? 1. Ar 2. CO 2 3. H 2 O correct 4. CH 4 5. 3 6. 4 Explanation: H 2 O has angular molecular geometry. It is assymetrical and polar. 003 10.0 points Which oF the Following elements would be ex- pected to have the highest electronegativity? 1. As 2. Li 3. Ge 4. Al 5. P correct Explanation: Electronegativity generally increases From leFt to right and From bottom to top oF the Periodic Table. 004 10.0 points Which oF the Following has bond angles oF exactly 120 ? 1. O 3 2. NO 2 3. S 2 3 4. HO 2 5. CS 2 3 correct Explanation: While CS 2 3 and NO 2 both have three re- gions oF electron density around the central atom, in NO 2 one oF these regions is a lone pair which will repel the other regions more strongly, making the bond angle less than
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Version 075 – Exam 2 – mccord – (50970) 2 120 . Only in CS 2 3 would the bond angle be exactly 120 . 005 10.0 points Identify the compound with the most polar bond. 1. PH 3 2. AsH 3 3. NH 3 correct 4. SbH 3 Explanation: Calculate the diFerence in the electronega- tivities (ΔEN): ΔEN As H 2 . 2 - 2 . 2 = 0 . 0 N H 3 . 0 - 2 . 2 = 0 . 8 P H 2 . 2 - 2 . 2 = 0 . 0 Sb H 2 . 2 - 2 . 1 = 0 . 1 The N H bond is the most polar of these. 006 10.0 points ICl 3 is sp 3 d hybridized. What is the electronic and molecular geometry? 1. tetrahedral; pyramidal 2. trigonal bipyramidal; T-shaped correct 3. octahedral; T-shaped 4. trigonal planar; trigonal planar 5. trigonal bipyramidal, seesaw Explanation: The hybridization tells us that there are 5 regions of high electron density. Three of those regions are the bonded Cl atoms. The other two regions must be lone pairs of elec- trons on the central I atom. This corresponds to trigonal bipyramidal electronic geometry
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exam 2 - Version 075 Exam 2 mccord (50970) This print-out...

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