Review Bonding

Chem I | Chem II AP
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1)
Atoms having greatly different electronegativities would be expected to form:
2)
Which of the following statements is INCORRECT?
A molecule with very polar bonds doesn't have to be polar as long as it is symmetrical so that the dipoles cancel out.
3)
In which pair do both compounds exhibit predominantly ionic bonding?
4)
Which of the following is not polar?
AsF5 is non polar because it is symmetrical and the dipoles cancel. ClF5 is polar because of the lone pair on the Cl which disrupts the symmetry.
5)
Which of the following has a dipole moment?
CH3Cl is the only molecule that has a dipole moment because it is the only molecule that doesn't have perfect symmetry so the dipoles will not exactly cancel. In SO3 all of the bonds are equal because of resonance.
6)
E in the structure at the right is a general symbol for a representative element.
Which of the elements below is represented by E?
This structure has 26 electrons. The oxygen atoms contribute 6 electrons each, the hydrogen atom contributes one electron, and the -2 charge indicates 2 more electrons in the structure than allowed by the atoms for a total of 21 electrons. This leaves 5 valence electrons for element E which means that it is in group 15, so it must be As.
Given the following Lewis structure:
Answer questions 7-9
7)
How many sigma and pi bonds:
Remember that each single bond is a σ bond and each double bond has one σ and one π. If there were a triple bond, it would contain 1 σ and 2 π bonds.
8)
How many carbon atoms involve sp2 hybridization?
Carbon #1-4 all have sp2 hybridization. Carbon # 5 is sp3 hybridized.
9)
What shape is involved in Carbon #1?
Carbon #1 has 3 BP and 0 LP so it must be trigonal planar.
10)
Which of the following molecules has the shortest bond length?

CO3-2 is trigonal planar and H2 is linear.

11)
Which of the following molecules has the shortest bond length?

Fluorine, nitrogen and oxygen have similar atomic radii, but the nitrogen molecule has a triple bond, which is shorter (and stronger) than the double bond in O2, which is shorter (and stronger) than the single bond in F2. Chlorine has a larger atomic radius than any of the others and it has a single bond, so it has the longest bond length.

12)
A Lewis structure for benzene is as follows:
Which of these statements is FALSE?
13)
Which of the following contains a pi bond?
14)
The hybridization of N in NO3- is:
15)
Given:
How many sigma and pi bonds does the molecule contain?
16)
Choose the statement that best describes GeCl4 molecule.
17)
How many of the following structures would be considered linear?
CO2
 
H2Se
 
HCl
 
SiCl2
 
O3
18)
In which case is the bond polarity CORRECT?
19)
Draw all possible resonance structures of each molecule. Circle the bond(s) in each molecule that are the longest.
a)
HNO3
The longest bond in this structure is the bond between nitrogen and the oxygen with the hydrogen attached. The bonds between nitrogen and the other two oxygen atoms are identical to each other and shorter than the other N-O-H bond because they have a bond order of 1.5. Based on the resonance structures, they are each shorter than a single (N-O) and longer than a double (N=O).
b)
C2H3O2-
The longest bond is the C-C bond. The C-H bonds are shorter because H has a smaller radius and so can get closer to the C. Both of the C-O bonds are identical and shorter than the C-C bond because they are a hybrid of a double and a single bond, which makes them shorter than a single bond and longer than a double.
c)
SO2
Both of the bonds in this molecule are identical. There is not one double bond and one single, but instead two identical bonds that are both a hybrid of a double and a single.
d)
CO3-2
All three of the bonds in this molecule have an identical length and a bond order of 1.3 because the double bond is shared evenly between all of the oxygen atoms.
20)
Assign a formal charge to all atoms in each structure below. Which diagram represents the most likely structure of the sulfate ion based on formal charge alone?
a)
b)
c)

Remember to calculate formal charge on any atom subtract the assigned electrons in the structure from the valence electrons. [Valence - Assigned] or [Should - Has]. Remember that each line counts as one and each dot counts as one.

In picture a), the sulfur has a formal charge of +2 and each of the oxygen atoms have a formal charge of -1, which gives an overall total charge of -2.

For sulfur in picture a) this is calculated by 6 valence - 4 assigned (4 lines) = +2 charge. For the oxygen atoms in picture a) the calculation is 6 valence - 7 assigned (6 dots and a line) = -1 charge.

In picture b), sulfur is 6 valence - 5 assigned (5 lines) = +1 charge and the double bonded oxygen is 6 valence - 6 assigned (4 dots and 2 lines) = 0 charge. The other three oxygen atoms are each -1 as calculated in picture a).

In picture c), sulfur is 6 valence - 6 assigned (6 lines) = 0 charge. The double bonded oxygen atoms are each 0 as calculated in picture b) and the single bonded oxygen atoms are each -1 as calculated in picture a).

Picture c) has the lowest overall formal charges, with charges on only 2 of the five atoms, so it is the most likely structure of the sulfate ion.

21)
Complete the following table:
COMPOUND/ION
LEWIS STRUCTURE
SHAPE
BOND ANGLE
HYBRID
DIPOLE MOMENT?
CCl2
SiH4
ClF4-
AsCl5
BeCl2
ICl2-
H3O+
HClO
22)
The yellow light given off by a sodium vapor lamp used for public lighting has a wavelength of 589 nm. What is the frequency of this radiation?
Hz
c = λ νso ν = c / λ
Wavelength is given in nm, which needs to be converted to meters so that the units will cancel with the speed of light.
589 nm x
1 m
1.0 x 109 nm
= 5.89 x 10-7 m
ν =
c
λ
=
3.0 x 108 m/sec
5.89 x 10-7 m
= 5.09 x 1014 sec-1 = 5.09 x 1014 Hz
23)
Calculate the energy (in kJ) of one photon of yellow light that has a wavelength of 589 nm.
kJ
E = hν = (6.626 x 10-34 J sec) (5.09 x 1014 sec-1) = 3.37 x 10-19 J
3.37 x 10-19 Jx
1 kJ
1000 J
= 3.37 x 10-22 kJ
24)
Calculate the energy (in kJ) of one mole of photons of yellow light that have a wavelength of 589 nm.
kJ
This is the same problem as the one before, it just asks for an entire mole of photons rather than just one.
6.02 x 1023 photons x
3.37 x 10-22 kJ
1 photon
= 203 kJ