Homework_6,Pt1(Answers)

Homework_6,Pt1(Answers) - HOMEWORK#6 PART 1 1 In H2 how...

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HOMEWORK #6, PART 1 1. In H 2 + , how many nodes does the ! 1s * orbital have along the internuclear axis? a. 0 b. 0.5 c. 1 d. 2 e. 3 Answer: c Looking at the wavefunction above, we see that the ! 1 s " has one node along the internuclear axis – this is the spot where the wavefunction crosses the internuclear axis resulting in an amplitude of zero at that point at all times, and a change of phase of the wavefunction from one side to the other. This node will take the form of a planar node between the two nuclei. See OGC_6 th ed_6.2.1 and p. 227 in particular. 2. If you excited the electron in H 2 + from the ! 1s state to the ! 1s * what would expect to happen to the molecule? a. It would eject an electron to become two H + ions b. It would vibrate c. It would contract to a shorter bond length d. It would dissociate into an H atom and H + ion e. It would become a Helium atom Answer: d The electron would occupy an antibonding orbital and this would cause the bond to break and give H and H + .
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3. Which of the following has the highest bond order O 2 , O 2 + , N 2 , N 2 + ? a. O 2 b. O 2 + c. N 2 d. N 2 + e. N 2 + and O 2 are the same and the highest Answer: c Calculate the bond order for each species using the appropriate MO diagram: O 2 : ! (10-6) = 2 O 2 + : ! (10-5) = 5/2 N 2 : ! (10-4) = 3 N 2 + : ! (9-4) = 5/2 Therefore N 2 has the highest bond order. See p.236 for N 2 and F 2 examples of MO correlation diagrams. 4. What is the bond order in Cl 2 ? a. 0.5 b. 1.0 c. 1.5 d. 2.0 e. 0.0 Answer: b By definition, Bond order BO= ! (Bonding electrons-Antibonding electrons) and we need to only consider the valence electrons in determining BO. The MO diagram for valence electrons of Cl 2 : ( ! 3s ) 2 ( ! * 3s ) 2 ( " 3p ) 4 ( ! 3pz ) 2 ( " * 3p ) 4 Therefore the bond order for Cl 2 = ! (8-6) = 1 5. If you remove one of the electrons from N 2 what will happen to its bond length? a. the bond length will increase b. the bond length will decrease c. the bond length will stay the same d. there will no longer be a bond in the molecule e. the bond length will be exactly half the original value Answer: a
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See question 3. We need to recognize that we are asked to compare the bond order of
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This note was uploaded on 04/30/2008 for the course CHEM 1411 taught by Professor Parkin during the Spring '08 term at Columbia.

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Homework_6,Pt1(Answers) - HOMEWORK#6 PART 1 1 In H2 how...

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