1. A Review of General Chemistry

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

e. HO—Br

f. H₃C—Li

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?

Rank the following compounds from highest dipole moment to lowest dipole moment:

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

In what direction is the dipole moment in calicene? Explain.

The C=O double bond has a dipole moment of about 2.4 D and a bond length of about 1.23 Å.

a. Calculate the amount of charge separation in this bond.

1. From what you remember of electronegativities, show the direction of the dipole moments of the following bonds.

2. In each case, predict whether the dipole moment is relatively large (electronegativity difference >0.5) or small.

a. C—Cl

b. C—H

c. C—Li

d. C—N

e. C—O

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

b. cis-1,2-dibromoethene or trans-2,3-dibromobut-2-ene

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

c. cis-1,2-dibromo-1,2-dichloroethene or cis-1,2-dichloroethene

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

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.

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.

e.

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.

Why are Na⁺ and K⁺ unable to form covalent bonds?

Show the ionic compound that you would expect to form between the given metal and nonmetal. Label the charges on each species.

(b) Mg and Br