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Ch. 8-9: Bonding AP Review Questions **Read attached notes on isomers and coordination compounds.** 1) A chemist analyzed the carbon-carbon bond in C 2 H 6 and found that it had a bond energy of 350 kJ/mol and a bond length of 1.5 angstroms. If the chemist performed the same analysis on the carbon-carbon bond in C 2 H 2 , how would the results compare? a) The bond energies and lengths for C 2 H 2 would be the same as those of C 2 H 6 . b) The bond energy for C 2 H 2 would be smaller and the bond length would be shorter. c) The bond energy for C 2 H 2 would be greater and the bond length would be longer. d) The bond energy for C 2 H 2 would be smaller and the bond length would be longer. e) The bond energy for C 2 H 2 would be greater and the bond length would be shorter. 2) 2 HI (g) → H 2(g) + I 2(g) For the reaction given above, ∆H o is –50 kJ. Based on the information given in the table below, what is the average bond energy of the H-I bond? Bond Average Bond Energy (kJ/mol) H—H 440 I—I 150 a) 270 kJ/mol b) 540 kJ/mol c) 590 kJ/mol d) 640 kJ/mol e) 1180 kJ/mol 3) Which of the following does not follow the octet rule? a) PCl 3 b) NO 2 c) CO 2 d) CO 3 2- e) HCO 3 1- 4) Which of the following violates the octet rule? a) NF 3 b) IF 3 c) PF 3 d) SbF 3 e) AsF 3 **Exceptions to Octet Rule: See #4 above: it does not follow the octet rule (too many e - ). It is stable, because it uses the empty "d" orbitals for hybrid orbitals. See #30: the NO does not follow the octet rule, since it has an unpaired electron. But it becomes stable by forming a dimer. Then all parts have 8 electrons!

AP Ch. 8-9 Structures Polarity Review Answers

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Page 1: AP Ch. 8-9 Structures Polarity Review Answers

Ch. 8-9: Bonding AP Review Questions **Read attached notes on isomers and coordination compounds.**

1) A chemist analyzed the carbon-carbon bond in C2H6 and found that it had a bond energy of 350 kJ/mol and a bond length of 1.5 angstroms. If the chemist performed the same analysis on the carbon-carbon bond in C2H2, how would the results compare?

a) The bond energies and lengths for C2H2 would be the same as those of C2H6.

b) The bond energy for C2H2 would be smaller and the bond length would be shorter.

c) The bond energy for C2H2 would be greater and the bond length would be longer.

d) The bond energy for C2H2 would be smaller and the bond length would be longer.

e) The bond energy for C2H2 would be greater and the bond length would be shorter.

2) 2 HI(g) → H2(g) + I2(g) For the reaction given above, ∆Ho is –50 kJ. Based on the information given in the table below, what is the average bond energy of the H-I bond? Bond Average Bond Energy (kJ/mol) H—H 440 I—I 150 a) 270 kJ/mol b) 540 kJ/mol c) 590 kJ/mol d) 640 kJ/mol e) 1180 kJ/mol

3) Which of the following does not follow the

octet rule? a) PCl3 b) NO2 c) CO2 d) CO3

2- e) HCO31-

4) Which of the following violates the octet rule? a) NF3 b) IF3 c) PF3 d) SbF3 e) AsF3

**Exceptions to Octet Rule: See #4 above: it does not follow the octet rule (too many e-). It is stable, because it uses the empty "d" orbitals for hybrid orbitals. See #30: the NO does not follow the octet rule, since it has an unpaired electron. But it becomes stable by forming a dimer. Then all parts have 8 electrons!

Page 2: AP Ch. 8-9 Structures Polarity Review Answers

5) Which of the following is expected to have the largest dipole moment?

a) CH4 b) CO2 c) SF6 d) HCN e) Cl-

6) The most polar of the following molecules is a) NH4

+ b) SO42- c) CF4

d) CH3CH2OH e) CH3CH2CHO

7) The most polar covalent bond is found

between which two elements based on the electronegativity of the elements?

a) C—N b) P—F c) S—O d) Si—C e) O—P

8) Under identical conditions, which of the

following gases is expected to deviate the most from ideal gas behavior?

a) oxygen b) nitrogen c) methane d) carbon dioxide e) water

9) A linear molecule can have the general formulas AA, AB, or AB2. Given a molecule with the general formula AB2, which one of the following would be the most useful in determining whether the molecule was bent or linear?

a) ionization energies b) electron affinities c) dipole moments d) electronegativities e) bond energies

10) Of the following molecules, which has the

largest dipole moment? a) CO b) CO2 c) O2 d) HF e) F2

Page 3: AP Ch. 8-9 Structures Polarity Review Answers

11) Which of the following contains nine sigma bonds and two pi bonds?

a) CCl2F2 b) HCN c) HCHO d) CH3COOH e) CH2CHCHCH2

12) Which of the following molecules has more

than one pi bond? a) CO2 b) SO2 c) NH3 d) C3H6 e) CH2O

13) The Lewis-Dot structure of an oxygen

molecule has a) one sigma bond b) one pi bond c) four nonbonded pairs d) (a), (b), and (c) e) (a) only

14) Which of the following is used to describe the

interaction of orbitals to form pi bonds?

15) Which of the following contains exactly 18

valence electrons? a) CO3

2- b) CO2 c) NO2 d) SO2 e) SO3

16) Which of the following has three resonance

structures? a) H2SO4 b) NO2

- c) SO3 d) HClO4 e) CO2

17) Which of the following has no resonance

structures? a) CO3

2- b) CO2 c) NO2 d) SO2 e) SO3

Page 4: AP Ch. 8-9 Structures Polarity Review Answers

18) The shape of CH4 is explained using a) VSEPR theory b) Hund’s Rule c) transition state theory d) quantum numbers e) Heisenberg’s uncertainty principle

19) The bond angles about the carbon atom in the

formaldehyde molecule, H2C=O, are approximately

a) 180 degrees b) 120 degrees c) 90 degrees d) 60 degrees e) 109 degrees

20) Which of the following is predicted to have a

square planar molecular structure? a) TeBr4 b) BrF3 c) IF5 d) XeF4 e) SCl2

21) According to VSEPR, the repulsion between

four regions of high electron density on a central atom are at a minimum when they

a) point to the four corners of a square b) point to the four corners of a rectangle c) have a tetrahedral geometry d) are arranged at 90 degrees to each

other e) have bi-pyramidal geometry

22) The geometry of the nitrate ion, NO3

-, is best described as a

a) tetrahedron b) trigonal bipyramid c) linear structure d) triangular planar structure e) square pyramid

23) How many of the following molecules have all of their atoms in the same plane?

CH2CH2 F2O H2CO NH3 CO2 BeCl2 H2O2 a) 3 b) 4 c) 5 d) 6 e) 7

24) Types of hybridization exhibited by the C

atoms in propene, CH3CHCH2, include which of the following?

I. sp II. sp2 III. sp3 a) I only b) III only c) I and II only d) II and III only e) I, II, and III

25) What is the percentage of s-character in sp3

hybrid orbitals? a) 25 b) 33 c) 50 d) 66 e) 75

Page 5: AP Ch. 8-9 Structures Polarity Review Answers

26) A molecule whose atoms are arranged linearly could have a central atom with which of the following hybridizations?

I. sp II. sp3 III. dsp3 a) I only b) II only c) I and II only d) I and III only e) I, II, and III

27) Which of the following does not form sp3

hybrid orbitals? a) carbon b) nitrogen c) hydrogen d) oxygen e) sulfur

28) Which of the following contains an atom with

sp3 hybrid orbitals? a) CH4 b) HCN c) H2 d) BH3 e) CO2

29) Which of the following has d2sp3 hybridization with no unshared pairs on the central atom? a) H2O b) NH3 c) CH4 d) SF6 e) XeF4

Questions 30-34 a) SO2 b) SiH4 c) CO2 d) Be2 e) NO 30) In which of the choices is there polar double bonding in a nonpolar molecule? 31) In which molecule(s) does resonance occur? 32) In which molecule is the bond order 2 ½? 33) Which of the molecules has four sp3 hybrid bonds? 34) Which molecule would you expect to be unstable on the basis of molecular orbital theory?

Page 6: AP Ch. 8-9 Structures Polarity Review Answers

35) An unknown substance is placed into a hot flame. The color of the flame is a bright red. Which of the following substances is most likely to be the unknown? a) Cu(NO3)2 b) NaCl c) KCl

d) LiCl e) Ba(NO3)2

36) The melting point of MgS is higher than that of KCl. Which of the following observations can explain this? I. Mg2+ has a greater positive charge than K+ II. S2- has a greater negative charge than Cl- III. S2- has a smaller radius than Cl- a) III only b) II and III only c) I and III only d) I and II only e) I, II, and III

Questions 37-40 a) CO2 b) H2O c) SO2 d) NO2 e) O2 37) In this molecule, oxygen forms sp3 hybrid orbitals. 38) This molecule contains one unpaired electron. 39) This molecule contains no pi (π) bonds. 40) This molecule is the main product of photosynthesis.

Page 7: AP Ch. 8-9 Structures Polarity Review Answers

Questions 41-43 a) Heisenberg uncertainty principle b) Shrodinger equation c) Hund’s Rule d) X-ray diffraction e) Photoelectric effect

41) Can be used to predict the paramagnetism of certain elements. 42) Predicts that it is impossible to simultaneously know both the location and momentum of an electron. 43) Predicts the locations and orientations of atomic orbitals.

44) Dimethylether (CH3 O CH3) and ethyl alcohol (CH3CH2OH) are examples of

a) position isomerism b) structural isomerism c) stereo isomerism d) (a) and (b) e) optical isomerism

45) What is the proper name of [Co(NH3)5Br]Cl2?

a) Cobaltpentaamine bromodichloride b) Pentaaminecobalt(III) bromodichloride c) Dichlorocobalt(V) bromodichloride d) Dichloropentaaminecobalt(III) bromide e) Pentaaminebromocobalt(III) chloride

Page 8: AP Ch. 8-9 Structures Polarity Review Answers

46) Which formula correctly represents the diamminediaquadibromochromium(III) ion?

a) [Cr(H2O)2(NH3)2Br2]+ b) [(NH3)2(H2O)Br2Cr]3+ c) [Cr(H2O)2(NH3)2Br2]3+ d) [(NH3)2(H2O)2Br2+Cr]+ e) [Cr(H2O)2(NH3)Br2]2+

47) Which of the following cannot be a complex ion? a) Fe(CN)6

3- b) Cu(NH4)42+

c) Co(Cl)64- d) AlF6

3- e) AgCl2

-

48) Which of the following is not a complex ion? a) Cr2O7

2- b) Ag(NH3)2+

c) FeCl63- d) Cd(CN)4

2- e) HgI4

2-

Page 9: AP Ch. 8-9 Structures Polarity Review Answers

Written Questions: 1) Give the total number of valence electrons in species. Indicate the number of valence

electrons on the central atom. Sketch and indicate the geometry of each of the following species. Give the approximate bond angles. Show unshared electron pairs only when they appear on the central atom.

a) BeF2 b) NO2

1- c) Br3

1- d) XeF4

Page 10: AP Ch. 8-9 Structures Polarity Review Answers

2) Oxygen is found in the atmosphere as a diatomic gas, O2, and as ozone, O3. a) Draw the Lewis structures for both molecules. b) Use the principles of bonding and molecular structure to account for the fact that ozone has

a higher boiling point than diatomic oxygen. c) Use the principles of bonding and molecular structure to account for the fact that ozone is

more soluble than diatomic oxygen in water. d) Explain why the two bonds in O3 are the same length and are longer than the bond length of

the bond in diatomic oxygen.

3) Interpret each of the following four examples using modern bonding principles. a) C2H2 and C2H6 both contain two carbon atoms. However, the bond between the two

carbons in C2H2 is significantly shorter than the bond between the two carbons in C2H6. b) The bond angle in the hydronium ion, H3O+, is less than 109.5o, the angle of a tetrahedron. c) The lengths of the bonds between the carbon and the oxygens in the carbonate ion, CO3

2-, are all equal and are longer than one might expect to find in the carbon monoxide molecule, CO.

d) The CNO- ion is linear.

Page 11: AP Ch. 8-9 Structures Polarity Review Answers

4) Consider the molecules PF3 and PF5. a) Draw the Lewis electron-dot structures for PF3 and PF5 and predict the molecular geometry

of each. b) Is the PF3 molecule polar, or is it nonpolar? Explain. c) On the basis of bonding principles, predict whether each of the following compounds exists.

In each case, explain your prediction. (i) NF5 (ii) AsF5

Page 12: AP Ch. 8-9 Structures Polarity Review Answers

5) Explain each of the following observations in terms of the electronic structure and/or bonding of the compounds involved.

a) At ordinary conditions, HF (normal boiling point = 20 oC) is a liquid, whereas HCl (normal boiling point = -114 oC) is a gas.

b) Molecules of AsF3 are polar, whereas molecules of AsF5 are nonpolar. c) The N—O bonds in the NO2

- ion are equal in length, whereas they are unequal in HNO2. d) For sulfur, the fluorides SF2, SF4, and SF6 are known to exist, whereas for oxygen only OF2

is known to exist.

Page 13: AP Ch. 8-9 Structures Polarity Review Answers

6) 10.00g of a compound containing only carbon and hydrogen is burned in an insufficient amount of oxygen to convert all the carbon to CO2. 12.86 g of water is formed along with 22.25 g of CO2. The only other substance left after the reaction is complete is CO.

a) What is the empirical formula of the hydrocarbon? b) How many grams of CO are formed? c) At 25 oC the 10.00 g sample of the hydrocarbon alone had a pressure of 0.873 atm in a 10.0

L container. What is the molar mass of the compound? What is the molecular formula of the compound?

d) Draw the Lewis structure for this compound and describe its geometry in words.