Unit 7 Mc Sizzle
Mr. Chakrabarty
TEACHER ANSWER KEY
December 12, 2009
1
1. Given the structural formula shown:
Which two formulas represent compounds that are isomers of each other?
1. A and B
3. B and D
2. A and C
4. C and D
1 Isomers are compounds that have the same molecular formula but different structural formulas.
Refer to the accompanying table: Clearly, formulas A and B have the same molecular formula and
are therefore isomers of each other.
1
2. A molecule of butane and a molecule of 2-butene both have the same total number of
1. carbon atoms
3. single bonds
2. hydrogen atoms
4. double bonds
1 See Reference Table P. The organic prefix but- stands for 4 carbon atoms. Therefore, molecules
of butane and 2-butene have the same number of carbon atoms.
2
3. Which general formula represents the homologous series of hydrocarbons that includes the
compound l-heptyne?
1. Cn H2n–6
3. Cn H2n
2. Cn H2n-2
4. Cn H2n+2
2 See Reference Table Q. The suffix -yne stands for the alkyne series of hydrocarbons, which has
the general formula Cn H2n -2.
4
4. Which organic compound is a saturated hydrocarbon?
1. ethyne
3. ethanol
2. ethene
4. ethane
4 A saturated hydrocarbon contains only carbon and hydrogen and is joined by only single bonds.
See Reference Table Q. Ethane is a saturated hydrocarbon.
Wrong Choices Explained:
(1) Ethyne contains a triple bond; it is an unsaturated hydrocarbon.
(2) Ethene contains a double bond; it is also an unsaturated hydrocarbon.
(3) See Reference Table R. Ethanol is an alcohol and is not a hydrocarbon.
2
5. Which two compounds are isomers of each other?
1. CH3CH2COOH and CH3COOCH2CH3
3. CH3CHBrCH3 and CH2BrCHBrCH3
2. CH3CH2CHO and CH3COCH3
4. CH3CHOHCH3 and CH3CHOHCH2OH
2 See Reference Table R. Isomers are compounds that have the same molecular formula but
different structural formulas. Of the choices given, only choice (2), CH3CH2CHO and CH3COCH3,
meets this requirement. Although both compounds have the same molecular formula (C3H6O), the
first compound is an aldehyde and the second is a ketone.
2
6. Which formula represents an unsaturated hydrocarbon?
2 An unsaturated hydrocarbon is a compound that contains only carbon and hydrogen atoms and
has at least one double or triple carbon-to-carbon bond. Of the choices given, only the structure
shown in choice (2) meets both requirements.
2
7. Hydrocarbons are compounds that contain
1. carbon, only
3. carbon, hydrogen, and oxygen, only
2. carbon and hydrogen, only
4. carbon, hydrogen, oxygen, and nitrogen, only
2 By definition, hydrocarbons are organic compounds that contain carbon and hydrogen, only.
3
8. The reaction that joins thousands of small, identical molecules to form one very long molecule is
called
1. esterification
3. polymerization
2. fermentation
4. substitution
3 In polymerization, individual molecules called monomers join chemically (by addition or
condensation) to form large, complex molecules known as polymers.
Wrong Choices Explained:
(1) In esterification, an alcohol and an organic acid react to produce water and the organic product,
which is classified as an ester.
(2) In fermentation, a sugar is converted by yeast enzymes into an alcohol and carbon dioxide.
(4) In substitution, an atom such as chlorine replaces an atom such as hydrogen (which is bonded to
a carbon atom in an organic compound).
2
9. What is the IUPAC name of the organic compound that has the formula shown below?
1. 1,1-dimethylbutane
3. hexane
2. 2-methylpentane
4. 4-methylpentane
2 The parent name of this molecule is pentane since the longest unbroken chain consists of 5
carbon atoms. The number of the carbon on which the methyl group (CH3–) is placed is 2 because
the parent chain is numbered in order to produce the smallest number, in this case, from right to
left.
1
10. Which compound is a member of the same homologous series as C3H8?
1. CH4
3. C5H8
2. C4H8
4. C5H10
1 Use Reference Table Q. C3H8 belongs to the alkane series of hydrocarbons, whose general
formula is CnH2n+2. Of the choices given, only choice (1), CH4, has this same general formula.
Wrong Choices Explained:
(2), (4) The general formula of these compounds is CnH2n. (3) The general formula of this
compound is CnH2n-2.
2
11. Which formula represents a molecule of a saturated hydrocarbon?
1. C2H2
3. C5H8
2. C4H10
4. C6H6
1
12. Molecules of 2-methyl butane and 2,2-dimethyl propane have different
1. structural formulas
3. numbers of carbon atoms
2. molecular formulas
4. numbers of covalent bonds
4
13. The molecule shown belongs to which class of compounds?
1. alcohol
3. aldehyde
2. ester
4. amino acid
1
14. Given the incomplete reaction: . . . (see image)
Which compound is represented by x?
4
15. Which structural formula represents a molecule that is not an isomer of pentane?
4 Isomers of a compound have the same molecular formula but different structural formulas. Refer
to Reference Tables P and Q. By using the general formula for alkanes (CnH2n+2), and setting n = 5,
we see that the molecular formula for pentane is C5H12. Now count the number of carbon and
hydrogen atoms in each choice. Of the choices given, only choice (4) (see image), does not have
the molecular formula C5H12. Therefore, this compound cannot be an isomer of pentane.
2
16. Which structural formula represents an alcohol?
2 Refer to Reference Table R. An alcohol contains the functional group -NOH.
Wrong Choices Explained:
(1) This compound is a ketone, known as propanone.
(3) This compound is an aldehyde, known as ethanal.
(4) This compound is an organic acid, known as ethanoic acid.
1
17. What is the IUPAC name of the compound with the structural formula shown?
1. 2-pentene
3. 2-pentyne
2. 3-pentene
4. 3-pentyne
1 Refer to the diagram (see image) and to Reference Tables P and Q :
Note that the hydrocarbon has one double bond, classifying it as an alkene. Its name will end in ene. Since the hydrocarbon has 5 carbon atoms, its name is pentene. Finally, note that the double
bond is positioned between carbons 2 and 3. (Count from right to left!) Since the lower number is
used, the IUPAC name is 2-pentene.
4
18. Given the structural formulas for two organic compounds (see image):
The differences in their physical and chemical properties are primarily due to their different
1. number of carbon atoms
3. molecular masses
2. number of hydrogen atoms
4. functional groups
4 Refer to Reference Table R. The organic compounds in this question are butanoic acid, an organic
acid, and methyl propanoate, an ester. Since the functional groups in these compounds are different,
they will have different physical and chemical properties.
2
19. Molecules of 1-bromopropane and 2-bromopropane differ in
1. molecular formula
3. number of carbon atoms per molecule
2. structural formula
4. number of bromine atoms per molecule
2 Examine the diagrams of 1-bromopropane and 2-bromopropane given (see image).
In 1-bromopropane, the bromine atom is bonded to the first carbon atom; in 2-bromopropane, the
bromine atom is bonded to the middle carbon atom. Clearly, the structures of the molecules are
different.
Wrong Choices Explained:
(1) Both compounds have the same molecular formula: C3H7Br.
(3) Both molecules contain 3 carbon atoms.
(4) Both molecules contain 1 bromine atom.
4
20. Given the three organic structural formulas shown (see image).
Which organic-compound classes are represented by these structural formulas, as shown from left
to right?
1. ester, organic acid, ketone
3. ketone, aldehyde, alcohol
2. ester, aldehyde, organic acid
4. ketone, organic acid, alcohol
4 Refer to Reference Table R, and compare the functional groups of the compounds with those
given in the table. The first compound is a ketone, the second is an organic acid, and the third is an
alcohol.
2
21. Given the equation:
X + Cl2 --> C2H5Cl + HCl
Which molecule is represented by X ?
1. C2H4
3. C3H6
2. C2H6
4. C3H8
2 The reaction given in this question represents a substitution reaction in which a Cl atom replaces
an H atom. The full reaction is shown below:
C2H6 + Cl2 --> C2H5Cl + HCl
2
22. Which formula represents an unsaturated hydrocarbon?
2 An unsaturated hydrocarbon is one that contains only carbon and hydrogen and has at least one
double or triple carbon-to-carbon bond. Of the choices given, only choice (2) meets these
requirements.
1
23. Given the formula: (see image)
What is the IUPAC name of this compound?
1. 2-pentene
3. 2-butene
2. 2-pentyne
4. 2-butyne
1 See Reference Tables P and Q. The hydrocarbon contains 5 carbon atoms and one double bond;
its name is pentene. Since the double bonds begins on the second carbon atom, the IUPAC name is
2-pentene.
1
24. Atoms of which element can bond with each other to form ring and chain structures in
compounds?
1. C
3. H
2. Ca
4. Na
1 Of the elements listed, only carbon (C) will bond with itself and form both ring and chain
structures.
2
25. Note: This question may require the use of the Reference Tables for Physical Setting/Chemistry.
Given the incomplete equation representing an organic addition reaction:
X(g) + Cl2(g) --> XCl2(g)
Which compound could be represented by X?
1. CH4
3. C3H8
2. C2H4
4. C4H10
2 Alkenes and alkynes (hydrocarbons containing double or triple carbon-to-carbon bonds,
respectively) can undergo addition reactions. See Reference Table Q. Of the choices listed, only
choice (2), C2H4, is an alkene. Wrong Choices Explained: (1), (3), (4) These hydrocarbons are
alkanes. They contain no double or triple bonds.
3
26. The compounds 2-butanol and 2-butene both contain
1. double bonds, only
3. carbon atoms
2. single bonds, only
4. oxygen atoms
3 See Reference Tables P, Q, and R. 2-butanol is an alcohol that contains 4 carbon atoms, 9
hydrogen atoms, and 1 oxygen atom. 2-butene is an alkene that contains 4 carbon atoms, 8
hydrogen atoms, and 1 double bond. Of the choices given, only choice (3), carbon atoms, describes
what both compounds have in common.
4
27. Which two compounds have the same molecular formula but different chemical and physical
properties?
1. CH3CH3Cl and CH3CH2Br
3. CH3CHO and CH3COCH3
2. CH3CHCH2 and CH3CH2CH3
4. CH3CH2OH and CH3OCH3
4 Isomers have the same molecular formula but different structural formulas. The chemical and
physical properties of isomers are necessarily different from one another. Of the choices given,
only the pair in choice (4), CH3CH2OH and CH3OCH3, have the same molecular formula (C2H6O)
and different structural formulas.
3
28. Which general formula represents the compound CH3CH2CCH?
1. CnHn
3. CnH2n - 2
2. CnH2n
4. CnH2n + 2
3 The molecular formula of this compound is C4H6, corresponding to a general formula of CnH2n-2.
Note that this compound is an alkyne.
2
29. Which class of organic compounds has molecules that contain nitrogen atoms?
1. alcohol
3. ether
2. amine
4. ketone
2 See Reference Table R. Organic compounds containing nitrogen can be classified either as
amines or as amides.
2
30. Which compound is a saturated hydrocarbon?
1. propanal
3. propene
2. propane
4. propyne
2 See Reference Table Q. A saturated hydrocarbon contains no double or triple bonds, and its name
ends with the suffix —ane.
2
31. The isomers butane and methylpropane differ in their
1. molecular formulas
3. total number of atoms per molecule
2. structural formulas
4. total number of bonds per molecule
2 Isomers are compounds that have the same molecular formulas but different structural formulas.
Both butane and methylpropane have the molecular formula C4H10. Their structural formulas are
shown in the accompanying diagram:
4
32. Which formula represents 2-butene?
4 See Reference Tables P and Q. The hydrocarbon 2-butene is a member of the alkene family. Its
molecular formula is C4H8. It has a double bond between carbons 2 and 3, as shown in the solution
diagram:
Wrong Choices Explained:
(1) The name of this hydrocarbon is butane; its molecular formula is C4H10.
(2) The name of this hydrocarbon is 1,3-butadiene because it has two double bonds.
(3) The name of this hydrocarbon is 1-butene.
4
33. Which compound is an alcohol?
1. propanal
3. butane
2. ethyne
4. methanol
3
34. In which reaction is soap a product?
1. addition
3. saponification
2. substitution
4. polymerization
4
35. Which structural formula is incorrect?
2
36. Which structural formula correctly represents a hydrocarbon molecule?
2 In order for a structure to represent a hydrocarbon molecule correctly, the molecule must contain
only carbon and hydrogen atoms, each carbon atom must be associated with 4 bonds, and each
hydrogen atom must be associated with 1 bond. Of the choices given, only choice (2) (see image)
meets all three criteria.
2
37. What is the total number of carbon atoms in a molecule of ethanoic acid?
1. 1
3. 3
2. 2
4. 4
2 See Reference Table P. The prefix eth– in ethanoic acid indicates that a molecule of this organic
acid contains 2 carbon atoms.
4
38. Given the formulas for two compounds:
These compounds differ in
1. gram-formula mass
3. percent composition by mass
2. molecular formula
4. physical properties at STP
4 See Reference Tables P and R. The first compound is diethyl ether, and the second compound is
1-butanol, an alcohol. The compounds are isomers because they have the same molecular formula
(C4H10O) but have different structural formulas. Since both compounds have different structures,
they have different physical (and chemical) properties.
Wrong Choices Explained:
(1), (2), (3) Both compounds have the same gram-formula mass and percent composition by mass
since they both have the same molecular formula.
3
39. Given the balanced equation (see diagram) with an unknown compound represented by X:
Which compound is represented by X?
1. CH3OH(aq)
3. CH3CH2OH(aq)
2. CH2(OH)4(aq)
4. CH2OHCH2OH(aq)
3 The equation represents the fermentation of glucose to alcohol and carbon dioxide. The same
number of carbon, hydrogen, and oxygen atoms must appear on both sides of this balanced
equation. On the left side are 6 carbon, 12 hydrogen, and 6 oxygen atoms. On the right side, the two
molecules of carbon dioxide use a total of 2 carbon and 4 oxygen atoms. The remaining atoms must
all be used by the unknown compound: 2X = C4H12O2; X = C2H6O. Of the choices given, only
choice (3), CH3CH2OH, corresponds to the molecular formula of X.
2
40. A double carbon-carbon bond is found in a molecule of
1. pentane
3. pentyne
2. pentene
4. pentanol
2 See Reference Table Q. An organic compound with a double carbon-carbon bond will add the
suffix –ene to its name, as in pentene.
Wrong Choices Explained:
(1) Pentane contains only single carbon-carbon bonds.
(3) Pentyne contains a triple carbon-carbon bond.
(4) Pentanol is an alcohol that contains only single carbon-carbon bonds.
4
41. Which compound is an unsaturated hydrocarbon?
1. hexanal
3. hexanoic acid
2. hexane
4. hexyne
4 An unsaturated hydrocarbon contains only carbon and hydrogen atoms and at least one double or
triple carbon-carbon bond. See Reference Tables Q and R. Of the choices given, only choice (4),
hexyne, is an unsaturated hydrocarbon. It contains six carbon atoms and one triple carbon-carbon
bond.
Wrong Choices Explained:
(1) Hexanal is an aldehyde. It contains carbon, hydrogen, and oxygen atoms.
(2) Hexane is a hydrocarbon. However, it is saturated because it contains only single carbon-carbon
bonds.
(3) Hexanoic acid is an organic acid. It contains carbon, hydrogen, and oxygen atoms.
2
42. The organic compound represented by the condensed structural formula CH3CH2CH2CHO is
classified as an
1. alcohol
3. ester
2. aldehyde
4. ether
2 See Reference Table R. The –CHO functional group is found in aldehydes.
1
43. Atoms of which element can bond to each other to form chains, rings, and networks?
1. carbon
3. hydrogen
2. fluorine
4. oxygen
1 Carbon is unique among the elements in that it can form a large number of chains (such as
polymers), rings (such as benzene), and networks (such as diamond).
4
44. Which structural formula represents an ether?
4 Refer to Reference Table R. An ether has the general formula R-O-R', where R and R' represent a
bonded carbon atom or a group of carbon atoms. The structural formula given in choice (4)
represents dimethyl ether.
Wrong Choices Explained:
(1) The structural formula given in this choice represents the aldehyde ethanal.
(2) The structural formula given in this choice represents the alcohol ethanol.
(3) The structural formula given in this choice represents the organic acid ethanoic acid.
1
45. Which element has atoms that can bond with each other to form long chains or rings?
1. carbon
3. oxygen
2. nitrogen
4. fluorine
1 Of the choices given, only choice (1), carbon, is unique in that its atoms can bond with each other
to form long chains or rings. The reasons for this uniqueness lie in the fact that carbon is located in
the middle group of the Periodic Table of the Elements, has four valence electrons, and can alter its
valence orbitals in a number of ways.
3
46. Which formula represents an unsaturated hydrocarbon?
1. C2H6
3. C5H8
2. C3H8
4. C6H14
3 An unsaturated hydrocarbon is one that contains a double or a triple bond (that is, an alkene or an
alkyne). See Reference Table Q. Of the choices given, only the formula for choice (3), C5H8,
matches the general formula (CnH2n-2) of an unsaturated hydrocarbon. The formula C5H8 represents
an alkyne.
WRONG CHOICES EXPLAINED:
(1), (2), (4) Each of these formulas matches the general formula (CnH2n+2) of an alkane, a saturated
hydrocarbon.
4
47. Which structural formula represents 2-pentyne?
4 Refer to Reference Tables P and Q. The prefix pent- indicates the presence of five carbon atoms.
The ending -yne indicates the presence of one carbon-carbon triple bond. Of the choices given,
only choice (4) meets both of these requirements.
2
48. Given the structural formula: (see image)
What is the IUPAC name of this compound?
1. propane
3. propanone
2. propene
4. propanal
2 See Reference Tables P and Q. The structural formula has three carbon atoms: it will have the
prefix prop-. Moreover, the formula contains one double bond: it will have the suffix -ene.
Therefore, the IUPAC name will be propene.
WRONG CHOICES EXPLAINED:
(1) Propane is the name of an alkane.
(3) Propanone is the name of a ketone; it is not a hydrocarbon.
(4) Propanal is the name of an aldehyde; it is not a hydrocarbon.
4
49. The three isomers of pentane have different
1. formula masses
3. empirical formulas
2. molecular formulas
4. structural formulas
4 Isomers of a compound have the same molecular formula (as well as the same empirical formula
and molecular mass) but different structural formulas.
2
50. Given the structural formula in the accompanying diagram:
The compound represented by this formula can be classified as an
1. organic acid
3. ester
2. ether
4. aldehyde
2 See Reference Table R. The formula corresponds to the general type R-O-R ', an ether. The name
of this compound is diethyl ether. The general formulas for the other choices (organic acid, ester,
and aldehyde) can also be found on Reference Table R.
2
51. Which formula represents a hydrocarbon?
1. CH3CH2CH2CHO
3. CH3CH2CH2COOH
2. CH3CH2CH2CH3
4. CH3CH2COOCH3
2 A hydrocarbon contains only the elements carbon and hydrogen. Of the choices given, only
choice (2), CH3CH2CH2CH3, contains carbon and hydrogen as its sole elements.
1
52. Which formula represents propyne?
1. C3H4
3. C5H8
2. C3H6
4. C5H10
1 See Reference Tables P and Q. The hydrocarbon propyne contains 3 carbon atoms and 1 triple
bond. Since the general formula for an alkyne is CnH2n-2, the formula for propyne must be C3H4.
4
53. The compounds CH3OCH3 and CH3CH2OH are isomers of each other. These two compounds
must have the same
1. density
3. melting point
2. reactivity
4. molecular formula
4 Isomers have the same molecular formula, but they have different structures and properties.
1
54. Which Lewis electron-dot diagram represents chloroethene?
1 Use Reference Tables P, Q, and R. A molecule of chloroethene must contain 1 chlorine atom
(chloro-), 2 carbon atoms (eth-), a double bond (-ene), and the correct number of hydrogen atoms
(3). Of the choices given, only choice (1) meets these four requirements.
Wrong Choice Explained:
(3) This incorrect structure has too many hydrogen atoms. As a result, each carbon atom has 10
electrons in its valence shell.
1
55. What is the IUPAC name for the compound that has the condensed structural formula
CH3CH2CH2CHO?
1. butanal
3. propanal
2. butanol
4. propanol
1 Use Reference Tables P, Q, and R. The compound has 4 carbon atoms (but-), no carbon-carbon
double or triple bonds (-an-), and is an aldehyde because it has a CHO functional group (-al). The
name of this compound is butanal.
2
56. Given the formula (see diagram):
This compound is classified as
1. an aldehyde
3. an amine
2. an amide
4. a ketone
2 Use Reference Table R. The functional group at the right end of the molecule (CONH2) defines
the compound as an amide.
3
57. Which element is present in all organic compounds?
1. H
3. C
2. He
4. Ca
1
58. When butane burns in an excess of oxygen, the principal products are
1. CO2 and H2O
3. CO and H2O
2. CO2 and H2
4. CO and H2
3
59. Which structural formula represents an isomer of 1-propanol?
3
60. Which structural formula represents an unsaturated hydrocarbon?
1
61. Which organic reaction produces rubber and plastics?
1. polymerization
3. saponification
2. esterification
4. fermentation
3
62. Which compounds are isomers?
1. CH3OH and CH3CH2OH
3. CH3CH2CHO and CH3COCH3
2. CH4 and CCl4
4. CH3CH2OH and CH3CH2COOH
2
63. Which functional group, when attached to a chain of carbon atoms, will produce an organic
molecule with the characteristic properties of an aldehyde?
4
64. Given the equation: . . . (see image)
Which type of reaction does this equation represent?
1. addition
3. polymerization
2. hydrogenation
4. substitution
3
65. Which formula represents an ether?
1
66. Which compound is classified as a hydrocarbon?
1. ethane
3. chloroethane
2. ethanol
4. ethanoic acid
4
67. Which formula is an isomer of butane?
1
68. Which pair of compounds are alcohols?
2
69. The process of joining many small molecules into larger molecules is called
1. neutralization
3. saponification
2. polymerization
4. substitution
4
70. Which hydrocarbon is saturated?
1. propene
3. butene
2. ethyne
4. heptane
3
71. Which compound is an isomer of pentane?
1. butane
3. methyl butane
2. propane
4. methyl propane
3
72. Given the formulas of four organic compounds: (see image)
Which pair below contains an alcohol and an acid?
1. a and b
3. b and d
2. a and c
4. c and d
4
73. Which type of reaction is represented by the equation (see image)?
1. esterification
3. saponification
2. fermentation
4. polymerization
3
74. Which element must be present in an organic compound?
1. hydrogen
3. carbon
2. oxygen
4. nitrogen
3 All organic compounds must contain carbon.
1
75. Which compound is a saturated hydrocarbon?
1. hexane
3. hexanol
2. hexene
4. hexanal
1 A hydrocarbon contains only carbon and hydrogen. A saturated organic compound contains only
carbon-carbon single bonds. The name of a saturated hydrocarbon will always end in -ane. Hexane
is a saturated hydrocarbon containing six carbon atoms.
Wrong Choices Explained:
(2) Hexene is a hydrocarbon that contains six carbon atoms and one carbon-carbon double bond.
(3) Hexanol is an alcohol, which contains oxygen in addition to carbon and hydrogen.
(4) Hexanal is an aldehyde, which contains oxygen in addition to carbon and hydrogen.
4
76. Given the reaction:
This reaction is an example of
1. fermentation
3. hydrogenation
2. saponification
4. esterification
4 In this reaction, an organic acid and an alcohol react to produce an ester and water.
Wrong Choices Explained:
(1) Fermentation is the oxidation of a sugar to produce an alcohol and carbon dioxide.
(2) Saponification is the reaction of a fat (an ester) with a base to produce soap.
(3) Hydrogenation is an addition reaction used to saturate organic compounds that are unsaturated.
1
77. Which of these compounds has chemical properties most similar to the chemical properties of
ethanoic acid?
1. C3H7COOH
3. C2H5COOC2H5
2. C2H5OH
4. C2H5OC2H5
1 Refer to Reference Table R. The properties of ethanoic acid, an organic acid, are due to the
presence of the -COOH (carboxyl) functional group. Of the choices given, only choice (1),
C3H7COOH, contains the carboxyl functional group.
Wrong Choices Explained:
(2), (3), (4) These compounds are, respectively, an alcohol, an ester, and an ether. Each of these
compounds has properties distinctly different from an organic acid.