CHAPTER 9 Problems: 4, 7, 10, 16, 20, 22, 28, 30, 36, 40, 52, 56, 66, 81, 84, 92, 104, 107
4) Discuss the basic features of the VSEPR model. Explain why the magnitude of the repulsion decreases in the following order: lone pair - lone pair > lone pair - bonding > bonding - bonding.
7) Predict the geometries of the following species using the VSEPR model:
a) PCl3 c) SiH4
b) CHCl3 d) TeCl4
10) Predict the geometry of the following molecules or ions using the VSEPR model.
a) CH3I c) H2S e) SO42-
b) ClF3d) SO3
16) The bonds in beryllium hydride (BeH2) are polar, but the permanent dipole moment of the molecule is zero. Explain.
20) Which of the molecules below is polar? You may assume bonds between different colors of atoms are polar bonds.
22) Use valence bond theory to explain the bonding in Cl2 and HCl. Show how the atomic orbitals overlap when a bond is formed.
28) Describe the bonding scheme of the AsH3 molecule in terms of hybridization.
30) Describe the changes in hybridization (if any) of the Al atom in the following reaction
AlCl3 + Cl- AlCl4-
36) What are the hybrid orbitals on the carbon atoms in the following molecules
a) H3C-CH3c) CH3-C=C-CH2OH e) CH3COOH
b) H3C-CH=CH2d) CH3CH=O
40) How many sigma and pi bonds are there in each of the following molecules?
52) Use molecular orbital theory to explain why the Be2 molecule does not exist.
56) Explain why the bond order in N2 is greater than in N2+, but the bond order in O2 is less than in O2+.
66) Describe the bonding in the nitrate ion (NO3-) in terms of delocalized molecular orbitals.
81) Which of the following molecules or ions is linear?
a) ICl2-c) OF2 e) CdBr2
b) IF2+d) SnI2
84) Cyclopropane (C3H6) has the shape of an equilateral triangle in which each carbon atom is bonded to two hydrogen atoms and two other carbon atoms. Cubane (C8H8) has the shape of a cube in which each carbon atom is bonded to one hydrogen atom and three other carbon atoms at each corner of the cube.
a) Draw Lewis structures for these molecules.
b) Compare the C-C-C angles in these molecules to the values predicted from sp3 hybridization of a carbon atom.
c) Based on your answer in b, would you expect the above molecules to be easy to make? Why or why not?
92) Write the ground state electron configuration for B2. Is the molecule diamagnetic or paramagnetic? Why?
104) Which of the following molecules or ions possesses a permanent dipole moment?
a) ClF2+ c) IF4+
b) ClF2- d) IF4-
107) The compound TCDD (2,3,7,8-tetrachlorodibenzo-pdioxin) is highly toxic.
The molecule gained considerable notoriety in 2004 when it was implicated in the attempted murder of a Ukranian politician.
a) Describe the geometry of the molecule. Does it have a permanent dipole moment? Explain.
b) How many pi bonds and how many sigma bonds are there in TCDD?
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