Forces Questions (Chem 20)
1. Draw the following bonds. Label the electronegativities, and label the charges (if any) on the ends of the bond. Classify the bon as ionic, polar covalent, or nonpolar covalent:
a) H and Cl
b) C and H
c) N and O
d) I and Br
e) Mg and S
f) P and H
2. Using electronegativity as a guide, classify the following bonds as ionic, polar covalent or non polar covalent.
a. the bond in HBr
b. the bond in LiF
c. a C-C bond in propane C5H8
3. List and order the bonds in the following substances according to increasing bond polarity. Provide your reasoning.
a. H2O, H2, CH4, HF, NH3, LiH, BeH2
b. PCl3, LiI, I2, ICl, RbF, AlCl3
c. CH3OH
d. CHFCl2
4. Predict the shape of the following molecules. Provide Lewis formulas and stereochemical formulas.
a. SIBr4
b. BF3
c. NCl3
d. SCl2
5. Predict the bond polarity for the following bonds. Use a diagram that includes the partial negative and positive charges and direction of the bond dipole:
a. C N in hydrogen cyanide
b. N=O in nitrogen dioxide
c. P-S in P(SCN)3
d. C-C in C8H18
6. Use Lewis formulas and VSEPR theory to predict the molecular shape of the following molecules. Include a stereochemical formula for each molecule:
a. H2S (g)
b. BBr3 (l)
c. PCl3 (l)
d. SiBr4 (l)
e. BeI2 (s)
7. Draw the Lewis formula and describe the shape of each of the following ions:
a. IO4-
b. SO32-
c. ClO2-
8. Predict the polarity of the following molecules:
a. dichlorofluoromethane, CHFCl2
b. ethene, C2H4
c. chloroethane, C2H5Cl
d. methylamine, CH3NH2
e. ethanol, C2H5OH
9. Various consumer products and books exist to help people remove greasy stains from clothing, carpets, etc. Discuss how a knowledge of polar and non-polar substances is related to the removal of these kinds of stains.
10. Which compound in each of the following pairs has stronger dipole-dipole forces than the other in their liquid or solid state? Provide your reasoning.
a. hydrogen chloride or hydrogen fluoride
b. chloromethane, CH3Cl, or iodomethane, CH3I
c. nitrogen tribromide or ammonia
d. water or hydrogen sulfide
11. Based upon London force theory, which of the following pure substances has the stronger London forces in their liquid or solid state? Provide your reasoning.
a. CH4 or C2H6
b. Oxygen or nitrogen
c. Sulfur dioxide or nitrogen dioxide
d. Methane or ammonia
12. Based upon dipole-dipole and London forces, predict where possible, which molecular substance in the following pairs has the higher boiling point. Provide your reasoning.
a. boron trifluoride or nitrogen trifluoride
b. chloromethane or ethane
13. For each of following compounds, evidence indicates that hydrogen bonds contribute to the attraction between molecules. Draw a Lewis formula using a dashed line to represent any hydrogen bond between 2 molecules of the substance.
a. H2O2
b. HF
c. CH3OH
d. NH3