AP Chem

Bonding Homework Answers

1. For each, tell the geometry, shape, and give two examples of molecules that exhibit the given coordination. Also, draw a 2-D Lewis structure and sketch a 3-D structure. Give the hybridization of the central atom.

  • BeH2
  • [BeF4]2-
  • SF6
  • [IO3]-
  • [IO4]-
  • [IO6]5-
  • [GaBr4]-
  • [NCS]-
  • [SnPh3]-
  • SO2
  • SO3
/
  • SOCl2
  • SO2Cl2
  • MeC≡N
  • HC≡CH
  • H2CCH2
  • CO2
  • [CO3]2-
  • [NO3]-
  • NH2-
  • XeOF4
  • [SbCl6]-
/
  • [H3O]+
  • [NH4]+
  • IF5
  • [AlCl6]3-
  • SbPh5
  • [SO4]2-
  • O3
  • Me2SO
  • PCl3

HIO, HIO2, HIO3, HIO4, H2SO3, H2SO4, H3PO4, SF3N, PCl3, PCl5, XeF4, XeF2, N2O, NO, NO2, N2O4, N2O5, HNO2, HNO3, POCl3, C2O42-, SF4, SF6, B2H6

2. Rank the following groups of metals from highest to lowest mp.

A. Li, Rb, Na, Cs Li, Na, Rb, cs

B. Na, Mg, Al Al, Mg, Na

C. Sc-Zn (give a general trend) highest in middle, lowest on ends

D. Look up the metals with the five lowest and five highest melting points

3. Why is hydrogen a diatomic gas while lithium is a metal? Li has lower ionization energy, allowing easier delocalization of electrons so they can participate in metallic bonding

4. Why does carbon not normally form C2 gas? (C2 can form in a controlled environment in labs.) Can form more bonds in its more common allotropic forms

5. Why does He2 not exist? Give an explanation using valence bond theory and another with molecular orbital theory. VB: Complete duet, bond order 0 by MO

6. Why did Nature choose carbon as the backbone for biomolecules? Why not silicon? Are shows like Star Trek fake when they have silicon based aliens? Why isn't oxygen or nitrogen used as the basis for life's molecules? Carbon can catenate infinitely and also forms four bonds allowing it to form the most diverse range of compounds. Can bond to most other elements easily

7. Why aren't diatomic iodine, chlorine, fluorine, or bromine found in nature? Too reactive

8. Why is methyl chloride (CH3Cl) more polar then methyl fluoride? Longer bond length

9. Why do you think the C-O double bond in acetamide (CH3CONH2) is longer than that of acetone (CH3COCH3)? Draw resonance forms and see that the carbonyl group has double and single character in acetamide while in acetone it’s double only

10. Which C-O double bond is longer, that of acetamide or that of methyl acetate (CH3COOCH3)? Acetamide because N donates better than O due to electronegativity

11. Why is ozone unstable? Puts + formal charge on at least one O, O-O single are weak O-O double are strong

12. Draw resonance structures and use principles of chemical structure to explain the trend in reactivity of substituted benzene towards electrophilic aromatic substitution. Trend: aniline>phenol>benzene>chlorobenzene>nitrobenzene aniline donates best, nitrobenzene pulls electron density out of the ring the best

13. Why does isooctane (2,2,4-trimethyl pentane) have a lower boiling point than straight chain octane? Greater surface area-volume ratio for straight chain compared to branched, more surface area means more places for dispersion forces to act

14. Explain the trend in reactivity towards electrophilic aromatic substitution: pyrrole>furan>thiophene. S is in n = 3 while N and O are in n =2 as is carbon. N is less electronegative than O and can donate electrons better

15. Use arrow pushing to show how chloride ion reacts with methyl iodide to form methyl chloride and iodide ion.

16. Look up the bond energies necessary to solve this problem. Calculate the energy of the reaction between ethene and chlorine to produce dichlorethane.

17. Draw Lewis structures for ethane, ethene (ethylene), and ethyne (acetylene). Rank the compounds in terms of C-C bond length, and bond strength. Also rank them in C-H bond strength and C-H bond strength, justify your answers. Ethyne is the strongest shortest bond, ethane is the longest weakest bond.

18. Why is iodine incapable of sustaining a radical reaction with methane or other hydrocarbons? C-I and H-I bonds are long and weak and don’t release enough energy to keep a reaction going.

19. Fill in the table:

Li2 / Be2 / B2 / C2
Can exist / y / n / y / y
# unpaired e- / 0 / 0 / 0 / 0
# paired e- / 2 / 4 / 6 / 8
B.O. / 1 / 0 / 1 / 2
Para or dia / d / d / d / d
Stable? / n / NA / n / n
N2 / O2 / F2 / Ne2
Can exist / y / y / y / n
# unpaired e- / 0 / 2 / 0 / 0
# paired e- / 10 / 10 / 14 / 16
B.O. / 3 / 2 / 1 / 0
Para or dia / d / p / d / d
Stable? / y / y / y / NA

20. For each give the geometry counting all electron pairs and the shape counting only atoms around the central atom: A = atom, X = lone pair:

AX, AX2, AX3AX2E, AX4, AX3E, AX2E2, AX5, AX4E, AX3E2, AX2E3, AX6AX5E, AX4E2

Shape: Linear, linear, trigonal planar, bent, tetrahedral, pyramidal, bent, trigonal bipramidal, see-saw, t-shaped, octahedral, square pyramidal, square planar

21. For each rank the melting points from highest to lowest:

A. Na, Li, Rb, Cs, K

B. Mg, Na, Al

C. Sc-Zn

D. Cu-Au Cu, Ag, Au

E. B, C, N, O, F, Li, Be, Ne

F. He, H2H2, He

G. H2O, NH3, CH4, BH3

H. CH4, CF4, CCl4, CI4

I. Bronze, copper

J. NaCl, NaF, Na2O, Na2S

K. MgO, NaCl MgO, NaCl

L. AlCl3, MgCl2 MgCl2, AlCl3

M. AlF3, AlCl3, AlBr3, AlI3

24. Why is fluorine more reactive than chlorine and oxygen? Short bond is weak, an exception due to repulsion in the small volume of the molecule. Also, reacts violently with most substances, releasing energy that helps other fluorine molecules react

25. Why is nitrogen unreactive? Triple bond is very strong

27. The heat of formation of HF, HCl, HBr, or HI is endothermic. Guess which one and explain. HI because H-I bond is long, not very polar and weak.

28. Acids donate H+ ions in solution. Rank these acids from weakest to strongest and explain.

A. HF, HI, HBr, HCl HF, HCl, HBr, HI

B. HNO2, HNO3Nitrous, nitric

C. HClO4, HClO3, HClO2, HClO Hypochlorous, chlorous, chloric, hyperchloric

D. HClO, HIO, HBrO HIO, HBrO, HClO

29. Why does water have a higher boiling point than HF despite the fact that HF is a more polar molecule? 2 sites for H-bonding on water, 1 for HF

30. Why is the boiling point of 2-propanol higher than that of propanone? H-bonding

31. How does soap work? Polar on one end, nonpolar on the other

32. Without looking up any information in a table, circle the molecule in each group that would have the highest boiling point. Explain your reasoning using your understanding of IMFs.

A. CH3CH2OH CH3CH2CH2OH HOCH2CH2OH glycol

B. CH3CH2OH CH3CH2NH2 ethanol

C

Pentanol

D. CH3CH2NHCH2CH3 CH3CH2CH2CH2CH3 amine

E.

alcohol