Exam 2 - McCord - Version 207 Exam 2 mccord(50970 This...

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Version 207 – Exam 2 – mccord – (50970) 1 This print-out should have 34 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. McCord CH301 001 10.0 points Which of the following elements would be ex- pected to have the highest electronegativity? 1. As 2. Li 3. Al 4. P correct 5. Ge Explanation: Electronegativity generally increases from left to right and from bottom to top of the Periodic Table. 002 10.0 points The energy diagram in this question is the molecular orbital diagram for a homonuclear diatomic molecule. The lines represent MO’s but the labels have been removed. Consider the following molecular orbital di- agram: a b c What are the names of the labeled orbitals, a through c, respectively? 1. σ 2 p 2 p 1 s 2. π 2 p 2 p 1 s correct 3. π 2 p 2 p 2 s 4. σ 2 p 2 p 2 s 5. π 2 p 2 p 1 s Explanation: 003 10.0 points Which of the following symbols is used to depict a partial positive charge? 1. λ + 2. σ + 3. ψ + 4. δ + correct 5. γ + 6. + Explanation: 004 10.0 points White phosphorus is composed of molecules of P 4 in which each P atom is connected to three other P atoms in the shape of a tetrahe- dron. Does it obey the octet rule? 1. Unable to determine 2. No 3. Yes correct Explanation: From the structure P P P P it does obey the octet rule.
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Version 207 – Exam 2 – mccord – (50970) 2 005 10.0 points Which is the most polar molecule? 1. BF 3 2. Ar 3. CO 2 4. CH 4 5. CF 4 6. H 2 O correct Explanation: H 2 O has angular molecular geometry. It is assymetrical and polar. 006 10.0 points How many σ and π bonds are in the molecule below? C C H N H H 1. 6 σ , 1 π 2. 6 σ , 2 π 3. 7 σ , 1 π 4. 5 σ , 2 π correct 5. 5 σ , 1 π Explanation: Sigma bonds are the first bond formed be- tween any two bonded atoms. Any subse- quent bond is a pi bond. 007 10.0 points Consider the following pairs A and B A 1 ) N N O A 2 ) N N O B 1 ) P O O O O 3 B 2 ) P O O O O 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 2 3. A 2 and B 2 4. A 1 and B 1 Explanation: A 1 ) N N O - 1 +1 0 A 2 ) N N O 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 0 - 1 - 1 - 1 0 3 B 2 ) P O O O O 0 0 - 1 - 1 - 1 3 The first structure is preferred for the same reason. 008 10.0 points A molecule has two lone non-bonded pairs of electrons on the central atom and four atoms bonded to the central atom. What is its molecular shape and its hybridization? 1. square planar; sp 3 d 2 correct 2. square planar; sp 3 3. tetrahedral; sp 3 4. square pyramidal; sp 3 d 2 5. tetrahedral; sp 3 d 2
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Version 207 – Exam 2 – mccord – (50970) 3 6. octahedral; sp 3 d 2 7. pyramidal; sp 3 Explanation: One way to solve is to draw a sample and determine HED. Since HED = 6, you know electronic geometry is octahedral.
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