CH241 Practice Exam #1
Study Homework as well!!
True/False Indicate whether the sentence or statement is true or false.
____ 1. Organic chemistry can be defined as the chemistry of carbon-containing compounds. ____ 2. Organic compounds can contain other elements such as oxygen or nitrogen. ____ 3. Organic compounds are always derived from a living source. ____ 4. An unlimited number of carbon atoms can bond together to form chains. ____ 5. Most organic compounds contain ionic bonds. ____ 6. There are more inorganic compounds than organic compounds. ____ 7. Most inorganic compounds have a higher melting point than organic compounds. ____ 8. Steric strain is due to repulsion between the electron clouds of atoms or groups ____ 9. Torsional strain is due to the repulsion between the bonding electrons of two atoms or groups ____ 10. Isomers always have the same empirical (molecular) formula. ____ 11. Isomers have identical physical and chemical properties. ____ 12. A Newman projection represents the rotation along a C-C bond ____ 13. Anti conformers are more stable than gauche conformers ____ 14. The steric strain in gauche butane is equal to one half the steric strain in the 1,3-diaxial interaction of the axial conformer of a monosubstituted cyclohexane. ____ 15. The axial equitorial equilibrium constant Keq for monosubstituted cyclohexanes is always greater than 1
1
Multiple Choice Identify the letter of the choice that best completes the statement or answers the question.
____ 16. Which of thee following elements is represented by this electronic configuration 1s2 2s2 2p5 ? a. C b. N
c. O d. F
____ 17. Ar, K+ and Cl- are "isoelectric elements" (elements with the same number of electrons) What orbital does the last electron occupy? a. 3s b. 3p
c. 3d d. 2p
____ 18. What is the electronic configuration of a carbocation (C+) ? a. 1s2 b. 1s2 c. 1s2 d. 1s2
2s2 2s2 2s2 2s2
2p1 2p2 2p3 2p4
____ 19. In methylamine (CH3NH3) the C-N bond has what charge on the nitrogen? a. +1 b. partial positive (δ+) c. partial negative (δ-) d. no charge ____ 20. Which of the following contains polar covalent bonds? a. Na2O b. NH3
c. H2 d. KF
____ 21. Which of the following has the largest dipole moment (µ) a. C-C b. C-O
c. C-H d. H-F
____ 22. What is the formal charge on the nitrogen in the following compound? H H H H C C N H H a. +2 b. +1
c. 0 d. -1 2
____23. Which statements about p orbital overlap is correct? a. b. c. d.
sigma (σ) bonds are formed by direct overlap along the central bond axis pi (π) bonds are formed by side-by-side overlap above and below the central bond axis neither a nor b both a and b
____ 24. Identify the correct statement. Cycloalkanes__________ a. can have as few as two carbons. b. are unsaturated hydrocarbons. c. have more hydrogens than straight chain alkanes with the same number of carbons d. these are all wrong ____ 25. What atomic orbitals form the covalent bonds in butane? a. b. c. d.
carbon p orbitals and hydrogen s orbitals carbon sp3 orbitals and hydrogen s orbitals neither a nor b both a and b
____ 26. Which of the following is a use for alkanes? a. b. c. d.
fuel lubricant solvent all of the above
____ 27. All of the members of the alkane series of hydrocarbons have the general formula a. b. c. d.
CnH2n CnHn CnH2n+2 CnH2n-2
3
____ 28. Which of the following structural formulas represents an unbranched alkane? a.
c.
b.
d.
____ 29. Which of the following compounds exhibits structural isomerism? a. b. c. d.
propane methane butane ethane
____ 30. How many structural isomers are possible for butane? a. 2 b. 3 c. 4 d. 5 ____ 31. Which of the following compounds is a structural isomer of 2 methylbutane? a. b. c. d.
propane w-methylpropone butane pentane
____ 32. A structural isomer of
is
a.
c.
b.
d.
4
____ 33. The name for the following compound is
a. b. c. d.
(2-methyl-2-tert-butyl)propane 2,2,3,3-tetramethylbutane di-tert-butane neooctane
____ 34. What is the best name for the following compound?
a. b. c. d.
4,7-diethyl-7-methylnonane 3-methyl-3,6-diethylnonane 2,4-diethyl-4-methyloctane 6,7-diethyl-2-methyloctane
____ 35. The IUPAC name for a. b. c. d.
is
2-ethylbutane 2-methylbutane 3-methylpentane 3-ethylbutane
____ 36. The compound a. b. c. d.
has the IUPAC name
4-isopropyloctane 5-isopropyloctane 5-sec-butyloctane 4-propyloctane
5
____ 37. The structural formula of 1-bromo-2,2-dimethylpropane is a.
c.
b.
d.
____ 38. A general formula for cycloalkanes is a. b. c. d.
C2H2n+2 CnH2n CnH2n-2 CnH2n-4
____ 39. The IUPAC name of position a. b. c. d.
contains an ethyl group located at
1 2 3 4
____ 40. A correct IUPAC name for a. b. c. d.
1-bromo-3-ethyl-1-methylcyclopropane 1-bromo-2-ethyl-1-methylcyclopropane 1-bromo-1-ethyl-2-methylcyclopropane 2-bromo-1-ethyl-2-methylcyclopropane
____ 41. The compound a. b. c. d.
is
is _____-1,2-dimethylcyclopropane.
cis trans tis crans
____ 42. Which of the following has an sp2 hybridized carbon? a. CH3+ b. CH3•
c. CH3:− d. none of these 6
____ 43. The lone pair electrons in methyl anion (CH3:−) occupy what orbital? c. sp2 d. sp3
a. s b sp .
____ 44. Which is the closest bond angle for C-O-C in CH3-O-CH3 a. 90° b. 109.5°
c. 120° d. 180°
____ 45. In the hydrogen halides the strongest bond is found in_____ and the longest bond is found in______ a. HCl, HI b. HBr, HF
c. HF, HI d. HI, HF
____ 46. What is the electronic configuration of a carbanion (C-) ? a. b. c. d.
1s2 1s2 1s2 1s2
2s2 2s2 2s2 2s2
2p1 2p2 2p3 2p4
____ 47. Which H-C bond is the shortest? a. H-CH2-CH3 b. H-C≡CH
c. H-CΗ=CH2 d. H-CΗ3
____ 48. What is the reason for the above answer? a. more s character in an s-sp bond b. more s character in an s-sp2 bond
c. more s character in an s-sp3 bond d. none of these
____ 49. Which of the following has a net dipole moment of zero (µ = 0) a. Cl
H
c. Cl
C C H b. Cl
C C Cl Cl
H d. Cl
C C H
Cl Cl H C C
H
H
H 7
____ 50. The conjugate base of H2O is______ a. H3O+ b. H2O
c. OHd. H2O2
____ 51. The conjugate acid of H2O is______ a. H3O+ b H2O .
c. OHd. H2O2
____ 52. Which species act as bases in the following reaction? H2SO4 + HNO3
1
a. 1 and 4 b 1 and 3 .
2
↔
H2NO3(+)
+ HSO4(-)
3
4
c. 2 and 3 d. 2 and 4
____ 53. In the following acid/base reaction: CH3OH + CH3NH(-) ↔ CH3O(-) + CH3NH2 If Keq >> 1 , we know that_____ a. b. c. d.
CH3OH is a much weaker acid than CH3NH2 CH3NH- is a much stronger base than CH3Oneither a nor b both a and b
____ 54. The pKa of phenol is 10. At neutral pH, what is the ratio of its acidic form to its basic form? a. 1:1000 b. 10:1
c. 100:1 d. 1000:1
____ 55. Which of the following is the strongest acid? a. HF b. HI
c. CH4 d. NH3
____ 56. Which of the following has the largest pKa? a. HF b. HI
c. CH4 d. NH3 8
____ 57. Which would you expect to be a stronger acid, CF3 SO3H or CH3 SO3H and why? a. b. c. d.
CF3 SO3H because its conjugate acid is more stable CF3 SO3H because its conjugate base is more stable CH3 SO3H because its conjugate acid is more stable CH3 SO3H because its conjugate base is more stable
____ 58. At what pH will 25% of a compound with pKa = 5.3 be in its basic form? a. 6.2 b. 8.4
c. 5.3 d. 4.8
____ 59. Rotational conformers of ethane have equivalent potential energy every_____ of rotation a. 60° c. 109.5° b. 90° d. 120° ____ 60. The differences in boiling points for the structural isomers of butyl alcohol is mostly due to______ a. b. c. d.
differences in hydrogen bonding differences in Van der Waals interactions differences in packing the solid structure none of these
____ 61. The differences in melting points for the structural isomers of butyl alcohol is mostly due to______ a. b. c. d.
differences in hydrogen bonding differences in Van der Waals interactions differences in packing the solid structure none of these
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Short Answer 62.
Draw all the possible ethers of molecular formula C4H10O
63.
Draw the structure for 3-ethyl-4-isopropyloctane
64.
What are all the structural isomers of pentane (C5H12) and account for their differences in boiling points.
65.
65.
Draw the most stable and unstable staggered Newman projections of isobutyl chloride.
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CH241_PE1 Answer Section TRUE/FALSE 1.
T
2.
T
3.
F
4.
T
5.
F
6.
F
7.
T
8.
T see p 90-91
9.
T see p 89
10.
T
11.
F
12. 13.
T see p 88 T see p 90
14. T Ugh! Its TRUE page 99 and homework #32 15.
See
T see page 99
MULTIPLE CHOICE 16. D 17.
B
18.
A
19.
C see section 1.3
20.
B see section 1.3
21.
D see section 1.3
22.
B see p 13
23.
D
24.
D
11
25.
B
26.
D
27.
C see section 2.1 -2.8
28.
B
29.
C see section 2.1 -2.8
30.
A see section 2.1 -2.8
31.
D see section 2.1 -2.8
32.
D see section 2.1 -2.8
33.
B see section 2.1 -2.8
34.
B see section 2.1 -2.8
35.
C see section 2.1 -2.8
36.
A see section 2.1 -2.8
37.
A see section 2.1 -2.8
38.
B see section 2.1 -2.8
39.
C see section 2.1 -2.8
40.
B see section 2.1 -2.8
41.
A
42.
A see p 32-33
43.
D see p 32-33
44.
B homework #53
45.
C see p 36
46.
C see p 6
47.
B see p37
48.
A see p37
49.
A see p38
50.
C see p39-40
51.
A see p39-40
52.
D see p39-40
53.
D see p44
54.
55. 56. 57.
58.
D neutral pH = 7, so the pKa of phenol (10) is 3 units more acidic, This means 3 factors of 10 tword the acidic form of phenol, so the ratio is (10X10X10):1 = 1000:1 A HI is the strongest due to its conjugate base (I-) stability C largest pKa = weakest acid, methane pKa = 60 B think about the conjugate bases of these acids, they have negative charges that can be stabilized by a good electron withdrawing group, and CF3, (also called triflate) does a much better job at this than CH3 D the Henderson-Hasselbalch equation on page 51 will give this answer, but it isn't necessary! Remember that at pH = pKa the acidic:basic ratio is 1:1 so at pH > pKa there is always more basic form than acidic form
59. 60. 61.
We want 25% basic (and 75% acidic) so more acidic than basic form and this will only happen at pH < pKa There is only one value of pH (4.8) that is less than the pKa (5.3) D see page 89 B see section 2.9 (p 81) C see section 2.9 (p 86)
SHORT ANSWER 62. H2 C
O
O
O
H 3C
H2 C O
CH 3
O
H2 C
H 3C
C H2
12
H3C
O H CH 3 C CH 3
CH 3
63. H2 C H 3C
C H2 H 3C
H2 C H C C C H H2
CH 3 C H
CH 3
C H2
CH 3
64. H2 C
H2 C C H2
H 3C
H 3C
C CH 3
H2 C H C
CH3 H 3C
CH3
B
C CH3
CH3
A
CH3
the interactions between molecules that maximize Van der Waals forces gives the highest boiling point, so the order of increasing boiling point is neopentane < isopentane < n-pentane (A < B < C)
65.
see chapter 2, #43 H3C
Cl CH 3
H
H least
H
H
Cl
CH3 H H CH3
most
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