1. A Review of General Chemistry

Rank the bonds from most polar to least polar.

d. C—H, C—C, C—N

Given the Lewis structures, indicate the direction of the dipole moment, if there is one.

(a)

For each alkene, indicate the direction of the dipole moment. For each pair, determine which compound has the larger dipole moment.

a. cis-1,2-difluoroethene or trans-1,2-difluoroethene

Which of the following molecules would you expect to have a dipole moment of zero?

g. BeCl₂

h. BF₃

Use the symbols δ⁺ and δ⁻ to show the direction of the polarity of the indicated bond in each of the following compounds:

c. H₃C—NH₂

d. H₃C—Cl

Show the direction of the dipole moment in each of the following bonds (use the electronegativities given in [Table 1.3] ):

a. H3C—Br

b. H3C—Li

For each of the following compounds,

1. draw the Lewis structure.

2. show how the bond dipole moments (and those of any nonbonding pairs of electrons) contribute to the molecular dipole moment.

3. estimate whether the compound will have a large, small, or zero dipole moment.

d.

After examining the potential maps for LiH, HF, and H₂, answer the following questions:

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a. Which compounds are polar?

b. Why does LiH have the largest hydrogen?

c. Which compound has the hydrogen that would be most apt to attract a negatively charged molecule?

For each of the following compounds,

1. draw the Lewis structure.

2. show how the bond dipole moments (and those of any nonbonding pairs of electrons) contribute to the molecular dipole moment.

3. estimate whether the compound will have a large, small, or zero dipole moment.

a. CH₃CH=NCH₃

b. CH₃CH₂OH

c. CBr₄

Which of the following compounds have a dipole moment of zero?

The N—F bond is more polar than the N—H bond, but NF₃ has a smaller dipole moment than NH₃. Explain this curious result.

NF₃

μ= 0.2 D

NH₃

μ = 1.5 D

Give the charge most likely to result from ionization of the following metals.

(b) Aluminum

The electrostatic potential maps for ammonia and water are shown here. The structure of ammonia is shown within its EPM. Note how the lone pair creates a region of high electron potential (red), and the hydrogens are in regions of low electron potential (blue). Show how your three-dimensional structure of water corresponds with its EPM.

Explain why HCl has a smaller dipole moment than HF, even though the H—Cl bond is longer than the H—F bond.