Organic Chemistry

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Chapter 1

MULTIPLE CHOICE QUESTIONS
Topic: Atomic Orbitals
1.
A)
B)
C)
D)
E)

In quantum mechanics a node (nodal surface or plane) is:
a place where Ψ is negative.
a place where Ψ is positive.
a place where Ψ = 0.
a place where Ψ2 is large.
a place where Ψ2 is negative.
Ans: C

Topic: Atomic Orbitals, Molecular Orbitals
2. When the 1s orbitals of two hydrogen atoms combine to form a hydrogen molecule, how many molecular orbitals are formed?
A) 1
B) 2
C) 3
D) 4
E) 5
Ans: B
Topic: Atomic Orbitals
3. Which principle(s) or rule must be used to determine the correct electronic configuration for carbon in its ground state?
A) Aufbau Principle
B) Hund's Rule
C) Pauli Exclusion Principle
D) (A) and (B) only
E) All three
Ans: E

1

Chapter 1

Topic: Atomic Orbitals, Bonding
4. What point on the potential energy diagram below represents the most stable state for the hydrogen molecule?

A)
B)
C)
D)
E)

I
II
III
IV
V
Ans: C

Topic: Atomic Orbitals, Molecular Orbitals
5.
A)
B)
C)
D)
E)

According to molecular orbital theory, which molecule could not exist? H2
He2
Li2
F2
N2
Ans: B

Topic: Atomic Orbitals, Molecular Orbitals
6. When the ls orbitals of two hydrogen atoms combine to form a hydrogen molecule, which molecular orbitals are formed?
A) One bonding molecular orbital only
B) Two bonding molecular orbitals
C) One bonding molecular orbital and one antibonding molecular orbital D) Two antibonding molecular orbitals
E) Three bonding molecular orbitals
Ans: C

2

Chapter 1

Topic: Atomic Orbitals, Hybridization
7. The following electron configuration represents _______.

A)
B)
C)
D)
E)

1s
2sp3 2sp3 2sp3 2sp3
the ground state of boron.
the sp3 hybridized state of carbon.
the sp3 hybridized state of nitrogen.
the ground state of carbon.
an excited state of carbon.
Ans: C

Topic: Atomic Orbitals, Molecular Orbitals
8. According to molecular orbital theory, in the case of a carbon-carbon double bond, the carbon-carbon bonding electrons of higher energy occupy this molecular orbital. A) σ bonding MO
B) π bonding MO
C) σ* antibonding MO
D) π* antibonding MO
E) π* bonding MO
Ans: B
Topic: Atomic Orbitals, Hybridization
9.
A)
B)
C)
D)
E)

Identify the atomic orbitals in the C-C sigma bond in ethyne. (2sp2, 2sp2)
(2sp3, 2sp3)
(2sp, 2sp)
(2p, 2p)
(2sp, 1s)
Ans: C

3

Chapter 1

Topic: Lewis Structures, Formal Charges
10. Listed below are electron dot formulas for several simple molecules and ions. All valence electrons are shown; however, electrical charges have been omitted deliberately.

H : Be : H

H
..
H:N:H
..

H
..
H:N:H
..
H

H
..
H:O:H
..

I

A)
B)
C)
D)
E)

H
..
H:B:H
..
H
II

III

IV

V

Which of the structures actually bear(s) a positive charge?
I
II
III
III & V
IV & V
Ans: E

Topic: Lewis Structures, Formal Charges
11. What is the formal charge on oxygen in the following structure? ..
H3C

O

CH3

CH3

A)
B)
C)
D)
E)

+2
+1
0
-1
-2
Ans: B

4

Chapter 1

Topic: Lewis Structures, Formal Charges
12. In which structure(s) below does the oxygen have a formal charge of +1?

..
H

O

H

H

..
..

O:

C

O

H

H

I

..
H

II

..
H

H3C

O

CH3

CH3

III

IV

s

A)
B)
C)
D)
E)

I only
II only
I and III
I and IV
I, III, and IV
Ans: E

Topic: Lewis Structures, Formal Charges
13. Which structure(s) contain(s) an oxygen that bears a formal charge of +1? ..
..
:O
:O
..
..
..
..
: O C O:
HC
H3C
O
H
H3C
O
CH3
C
: O. :
: O. : : O. :
.
.
.
CH3
H
I
II
III
IV
V
A)
B)
C)
D)
E)

I and II
III and IV
V
II
I and V
Ans: B

5

Chapter 1

Topic: Lewis Structures, Formal Charges
14. Which of the following molecules or ions has a nitrogen with a formal charge of -1? (Charges on ions have been omitted.)
..
A) : N H
H

B) H
C) H

..
N

.H...
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