Exam April 2017, answers PDF

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Answers for assignment 8 for CHEM 104...

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CHEM 104-001 Assignment 8 Due Wednesday, March 22, 2017

Name: ________KEY_______________

(Total 81 points) 1. For the following molecules and ions, draw the Lewis structure. Determine the number of electron domains, the electron-domain geometry, and the molecular geometry. (50 points) (a) BeF2

(b) PH3

Number of electron domains:

2

Number of electron domains: 4

Electron domain geometry:

linear

Electron domain geometry:

tetrahedral

Molecular geometry:

linear

Molecular geometry:

trigonal pyramidal

(c) BCl3

(d) H2Te (note: Te is the central atom)

Electron domain geometry:

trigonal

Electron domain geometry:

tetrahedral

Molecular geometry:

trigonal

Molecular geometry:

bent

(e) PCl5

(f) BrF3

Number of electron domains:

5

Number of electron domains:

5

Electron domain geometry: trigonal bipyramidal

Electron domain geometry: trigonal bipyramidal

Molecular geometry:

Molecular geometry:

trigonal bipyramidal

e1o

T-shaped

Number of electron domains:

Number of electron domains:

6

Electron domain geometry: trigonal bipyramidal

Electron domain geometry:

octahedral

Molecular geometry: see-saw or disphenoidal

Molecular geometry:

square planar

(i) XeF4

(j) KrF2

5

Number of electron domains:

6

Number of electron domains:

Electron domain geometry:

octahedral

Electron domain geometry: trigonal bipyramidal

Molecular geometry:

square planar

Molecular geometry:

5 linear

2. Based on the molecular geometry of the molecules from question 1, which of the following molecules are polar? Circle the polar molecules. (4 points)

BeF2

NH4+

H2Te

Page 2 of 4

BrF3

3. Determine if the following orbital combinations will lead to a  (sigma) bond, a  (pi) bond, or no bond. (10 points) a. 2s + 2s

Answer:

b. 2s + 2pz (internuclear distance lies along the z-axis ) Answer:

 (sigma)

 (sigma)

c. 2py + 2py (internuclear distance lies along the z-axis)

Answer:

 (pi)

d. (2pz, 2pz) (internuclear distance lies along the z-axis)

Answer:

 (sigma)

e. (2py, 2pz) (internuclear distance lies along the z-axis)

Answer:

no bond

Page 3 of 4

3. The Lewis structure for an organic molecule is shown:

a. What is the hybridization of each carbon atom (labeled 1 to 4)? (4 points) 1. sp3

2. sp2

3. sp3

4. sp

b. How many  bonds and how many  bonds are there in the molecule? (2 points)  bonds:

 bonds:

12

3

c. What are the angles at a, b, and c? (ignore distortions and give ideal angles) (3 points)

a. 109.5

b. 120

c. 180

4. Give names for the following molecular geometries and bond angles. (8 points)

a. tetrahedral b. 109.50

b. octahedral 900

c. see-saw or disphenoidal 1200 and 900

Page 4 of 4

d. trigonal pyramidal 109.50...