Workbook on Bonding, Lewis Structures, VSEPR
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Bond
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Energy in kJ/mol
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C-C
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347
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C-N
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305
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C=N
CN
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615 891
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C-H
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413
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C=O
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745
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C=O (in CO2)
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799
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N-H
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391
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N-N
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160
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N-O
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201
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N=N
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418
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H-H
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432
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H-O
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467
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O=O
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498
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6. Using bond energies above, calculate the enthalpy for the combustion of 1 mole of butane to make carbon dioxide and water vapor. Start with a balanced equation and then draw Lewis Structures!
Lattice Energy
Draw an energy level diagram that illustrates the Born Haber Cycle for CsBr. All the necessary enthalpy values are given below, in no particular order. Use this cycle to calculate the lattice energy for CsBr, and then compare it to the lattice energy for LiF (determined in class).
Which of the following would you expect to have the highest magnitude of its lattice energy? Explain your choice clearly in terms of Coulomb's Law. LiI MgF2 RbBr CaS
Chem 127
INTERmolecular Forces (IMFs) Workbook
9. Check (?) whether each of the following materials is polar or nonpolar.
a)
Dr. Dettmar
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species
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polar
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nonpolar
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CO2
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PCl3
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CH4
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SF4
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BF3
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SO2Cl2
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b) List the dominant IMF in each of the following substances:
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Dominant IMF?
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pentane
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methanol
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octanol
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water
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ammonia
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hydrochloric acid
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carbon tetrachloride
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CHCl3 (chloroform)
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sodium chloride
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Chem 127 Dr. Dettmar
10.a) What does the term "polarizable" mean? What is the relationship between the size of a molecule and how easy it is to polarize?
- a) SO...which should have stronger dispersion forces, I2 or F2? Why? (And, by the way, in what states do these substances naturally occur?)(see a connection...?)
- b) Hydrocarbons are molecules that contain C and H atoms only. Because the difference in electronegativity between these atoms is very low, hydrocarbons are generally considered to be non-polar molecules. Given the following molecules:
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Molecules
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Molecular Mass
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CH3CH3 (ethane)
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CH3CH2CH3 (propane)
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CH3CH2CH2CH3 (butane)
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c) Whichistheeasiesttopolarize?
d) WhichhastheweakestIMFs?
11. H2S, O2 and CH3OH all have comparable molecular masses. Rank the strength of the IMFs that occur in pure samples of each of these compounds (1 = strongest, 2 = in between, 3 = weakest).
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Substance
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Dominant IMFs
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Relative Strength
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H2S
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O2
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CH3OH
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12. a) What are the requirements for the especially strong type of intermolecular force called hydrogen bonding?
Chem 127 Dr. Dettmar
b) Identify which of the following compounds will experience hydrogen bonding between its molecules? Briefly explain your choices, as well as why the other species couldn't hydrogen bond.
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Substance
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Yes/No
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Why
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CH3NH2
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HCl
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H2
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CH3CH2OH
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CH2O
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H2S
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13.a) Circle the species that you would expect to have the desired property and briefly explain your choice.
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Property
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Species
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WHY?
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More viscous
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CH3CH2CH2CH2OH or CHCl3
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Higher Boiling Pt
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Br2 or H2Se
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More likely to condense to liquid
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Br2 or F2
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SMALLER difference in energy between gas and liquid
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2-propanone or 1- propanol
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More volatile liquid
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Hexane or decane
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b) Complete the following:
"If the IMFs between the molecules of a liquid are relatively weak, then the boiling point of
the liquid will be relatively (high or low), the enthalpy of vaporization of the liquid will be relatively (high or low), the vapor pressure of the liquid
will be relatively
considered to be (more or less) volatile."
(high or low), and the liquid would be