Chemistry 1B Winter 2016 MWF 9:30
Midterm 2
Test Form A
For all Lewis structures, be sure to minimize the distribution of formal charge.
1.
Predict the formula of an ionic compound formed by strontium and iodine
A) SrI
B) Sr2I
C) SrI2
D) Sr2I3
E) Sr3I2
ANS: C
2.
Predict the formula of an ionic compound formed by antimony (Sb) and oxygen
A) SbO
B) Sb2O
C) SbO 2
D) Sb2O 3
E) Sb3O 2
ANS: A, B, C, or D
3.
For the elements Rb, F, and O, the order of increasing electronegativity is
A) Rb < F < O
B) Rb < O < F
C) O < F < Rb
D) F < Rb < O
E) none of these
ANS: B
4.
Which of the following bonds is the least polar? The electronegativity of H is lower than that of C.
A) H–F
B) H–N
C) H–O
D) H–C
E) All are the same.
ANS: D
5.
Which of the following elements forms the most ionic bond with chlorine?
A) Cs
B) Ga
C) P
D) Ar
E) I
ANS: A
6.
-
The nitrate ion NO 3 has ___ total electrons and ___ valence electrons.
A) 24, 24
B) 31, 23
C) 32, 32
D) 32, 24
E) 33, 25
ANS: D
7.
Among the following molecules, which has no dipole moment?
A) CO 2
B) H 2O
C) SF2
D) NCl3
E) ICl3
ANS: A
8.
How many electrons are in the Lewis structure for NO 2–?
A) 16
B) 30
C) 32
D) 20
E) 18
ANS: E
9.
As indicated by Lewis structures, which of the following species would not exist as a stable
molecule?
A) NH 3
B) N 2H 2
C) N 2H 6
D) N 2H 4
E) N 2O 4
ANS: C
10.
–
In the Lewis structure for Br3 , there are ____ lone pairs around the central bromine atom.
A) 1
B) 2
C) 3
D) 5
E) 6
ANS: C
11.
Which species has a single unpaired electron?
A) N 2
B) NO
C) CO
D) OH –
E) none of these
ANS: B
12.
Which molecule or ion is an exception to the octet rule?
A) I3–
B) NO 3–
C) PF3
D) H 2O
E) none of these
ANS: A
13.
In the Lewis structure for BF3
A) one F forms a double bond with B
B) there are three lone pairs on each F, and one lone pair on B
C) there are three equivalent resonance structures
D) the formal charge on each F is -1
E) there are three equivalent single bonds to the B
ANS: E
14.
Select the correct molecular structure for Br3–.
A) linear
B) bent
C) pyramidal
D) tetrahedral
E) T-shape
ANS: A
15.
VSEPR theory predicts that the bond angles about the carbon atom in the molecule,
Cl2C =O, are about
A) 120°
B) 60°
C) 109°
D) 180°
E) 90°
ANS: A
16.
What type of structure does the XeOF2 molecule have?
A) trigonal pyramid
B) tetrahedral
C) T-shaped
D) trigonal planar
E) octahedral
ANS: C
17.
Select the correct molecular structure for NO 3–.
A) trigonal pyramid
B) tetrahedral
C) square planar
D) octahedral
E) trigonal planar
ANS: E
18.
Select the correct molecular structure for PO 43–.
A) pyramidal
B) tetrahedral
C) square planar
D) octahedral
E) none of these
ANS: B
19.
In the molecule SF6, the formal charge on sulfur atom is
A) 0
B) 1
C) 2
D) 6
E) none of these
ANS: A
20.
The molecule ozone, O 3, has a bent structure. The formal charge on the central oxygen atom is
A) -1
B) 0
C) +1
D) +2
E) cannot be determined
ANS: C
21.
What is the hybridization of S in the molecule H2S?
A) sp
B) sp2
C) sp3
D) dsp3
E) d2sp3
ANS: C
22.
What is the hybridization of I in the molecule IF 3?
A) sp
B) sp2
C) sp3
D) dsp3
E) d2sp3
ANS: D
23.
Second row of the periodic table elements that are sp3 hybridized, are capable
of forming ____ pi bond(s).
A) 0
B) 1
C) 2
D) 3
E) 4
ANS: A
24.
What is the hybridization of the central atom in PCl4+?
A) sp
B) sp2
C) sp3
D) dsp3
E) d2sp3
ANS: C
25.
What is the hybridization of the carbon atom in CO 2?
A) sp
B) sp2
C) sp3
D) dsp3
E) d2sp3
ANS: A
26.
Consider the following molecule. (Lone pairs are not drawn in.)
H
C
H
C
C2
C1
H
O
H
C
C
C3
C4
C
N
C5
H
Specify the hybridization of each carbon atom (in numeric order: C1 C2
C3 C4 C5).
A)
B)
C)
D)
E)
sp2
sp2
sp2
sp2
sp
sp2
sp2
sp2
sp2
sp
sp2
sp2
sp3
sp3
sp
sp3
sp3
sp3
sp3
sp2
sp
sp3
sp
sp3
sp
ANS: A
27.
Which of the following has two pi bonds?
A) C 2H 6
B) C 2H 4
C) C 2H 2
D) at least two of these
E) none of these
ANS: C
28.
This molecule has
H
H
C
C
N
H
A) 7 sigma and 0 pi bonds
B) 6 sigma and 1 pi bonds
C) 5 sigma and 1 pi bonds
D) 4 sigma and 3 pi bonds
E) 5 sigma and 2 pi bonds
ANS: E
29.
BF3 reacts with NH3 to form F3B-NH 3. Upon forming this product, the B atom
A) remains with sp2 hybridization
B) changes hybridization from sp 2 to sp3
C) changes hybridization from sp 3 to sp2
D) atoms never change hybridization during a reaction
E) remains with sp3 hybridization
ANS: B
30.
This doubly charged anion to the right has, in total
A) no resonance structures
B) two resonance structures
C) three resonance structures
D) four resonance structures
E) five resonance structures
O
O
C
C
O
ANS: D
31.
Of these molecules, CH 4, NH 3 and H 2O, which has the smallest H-X-H bond?
A) CH 4
B) NH 3
C) H 2O
D) all are sp3 hybridized and therefore have the same bond angle
E) cannot determine from the information given
ANS:C
O
2-
32.
-
Because of the resonance structures in the nitrate ion, NO3 , each bond between the nitrogen and
oxygen can be considered
A) strictly a single bond
B) strictly a double bond
C) a pi bond
D) a sigma bond
E) a bond with both single and double bond character
ANS: E
33.
The methylene radical CH 2 is paramagnetic and has an approximate bond angle of 120˚. From these
data we can postulate
A) the molecule has sp2 hybridization with a lone pair in an sp2 orbital
B) the molecule has sp2 hybridization with one electron in an sp2 orbital and the other in a p orbital
C) the molecule has sp3 hybridization with two orbitals each containing a single electron
D) the molecule has sp3 hybridization with a lone pair in an sp3 orbital
E) the carbon atom has unhybridized orbitals
ANS: B
34.
A pi bond is distinct from a sigma bond because
A) a pi bond has no wavefunction density on the axis between the two atoms
B) a pi bond hinders rotation between the bonding atoms
C) a pi bond has maximum and equal wavefunction density above and below the bonding plane
D) a pi bond typically requires overlap of p orbitals
E) all of the above
ANS: E
35.
The Lewis structure for BeH 2 suggests
A) the Be atom has two unfilled 2p orbitals
B) the molecule has a bent structure
C) has an octet around the Be atom
D) has resonance structures
E) has a dipole moment
ANS: A
36.
For fluoromethane, shown in the orientation to the right, what is the direction of the dipole moment?
A) "
F
B) f
C) #
C
D) i
H
H
E) has no dipole moment
H
ANS: C
37.
-
The Lewis structure of the perchlorate ion ClO 4 results in ___ double bonds to the Cl atom.
A) 0
B) 1
C) 2
D) 3
E) 4
ANS: D
38.
+
What is the formal charge on the phosphorus atom in tetramethylphosphonium cation P(CH 3)4 ?
A) 0
B) +1
C) -1
D) +2
E) cannot be determined
ANS: B
39.
Molecular orbital theory applied to the diatomic molecule OF uses the following energy level
ordering
(σ2s) (σ2s*) (σ2p) (π2p) (π2p*) (σ2p*)
From this, we find that OF has
A) one unpaired electron, and a bond order of 3/2
B) one unpaired electron, and a bond order of 2
C) no unpaired electrons, and a bond order of 3/2
D) one unpaired electron, and a bond order of 1/2
E) none of these
ANS: A
40.
+
Molecular orbital theory applied to HeH predicts this species will
A) be unstable
B) be stable and paramagnetic
C) be stable with a bond order of 1/2
D) be stable with a bond order of 1
E) be stable with a bond order of 3/2
ANS: D