Block 3 training exercises.
Draw the Lewis structures for each of the following molecules and determine the electron pair
geometry and the molecular geometry as predicted by the VSEPR.
1) F2
2) N2
3) ICL
4) CO2
5) NH3
6) CF4
7) C2H6
8) C2H4
9) C2H2
10) HCN
11) SO2
12) HNO3 (the hydrogen is bonded to one of the oxygens).
13) CH4O
For each of the following polyatomic ions, draw all resonance structures. Based on the formal
charges identify which is the best resonance structure. (if all resonance structures are equivalent
indicate so next to the structure). Indicate the bond angles as predicted by VSEPR for the best
structure .
14) OH15) CN16) ClO2
–
17) ClO3
–
18) CO3
2-
19) SO3
2-
20) SCN-
21) HCO2
–
22) NO2
+
State the hybridization of each of the central atom in each of the following.
23) ClO2
–
24) ClO3
–
25) CO3
2-
26) SO3
2-
27) SCN28) HCO2
–
29) NO2 –
30) Hydrogen Peroxide (H2O2) is a reactive molecule, often used an antiseptic and sometimes
used for bleaching. Draw a Lewis structure for hydrogen peroxide (peroxide is a
polyatomic ion). What is the oxidation state of the oxygen in hydrogen peroxide?
Suggest a reason for its reactivity.
31) What is the hybridization of the central atom in Acetone CH3COCH3?
32) How many sigma bonds and how many pi bonds are in Acetone?
33) Ozone (O3) is needed in the stratosphere to absorb (and filter out) potentially damaging
ultraviolet light. However, in the lower atmosphere is a dangerous pollutant as it is a very
reactive form of oxygen and as a result, very toxic and destructive. Draw the two
reasonable structures, include formal charges. (Hint: it is not a ring) Suggest a reason for
its high reactivity
34) Which of the following reactions is associated with the lattice energy of Li2O (ΔH°latt)?
A) Li2O(s) → 2 Li⁺(g) + O2⁻(g)
B) 2 Li⁺(aq) + O2⁻(aq) → Li2O(s)
C) 2 Li⁺(g) + O2⁻(g) → Li2O(s)
D) Li2O(s) → 2 Li⁺(aq) + O2⁻(aq)
35). Which of the following reactions is associated with the lattice energy of CaS (ΔH°latt)?
A) Ca(s) + S(s) → CaS(s)
B) CaS(s) → Ca(s) + S(s)
C) Ca2⁺(aq) + S2⁻(aq) → CaS(s)
D) Ca2⁺(g) + S2⁻(g) → CaS(s)
E) CaS(s) → Ca2⁺(aq) + S2⁻(aq)
36). Which of the following reactions is associated with the lattice energy of RbI (ΔH°latt)?
A) Rb(s) +
2
1
I2(g) → RbI(s)
B) RbI(s) → Rb⁺(g) + I⁻(g)
C) RbI(s) → Rb(s) +
2
1
I2(g)
D) RbI(s) → Rb⁺(aq) + I⁻(aq)
E) Rb⁺(g) + I⁻(g) → RbI(s)
37). Which of the following NaCl, KCl, LiCl, CsCl has the highest magnitude of lattice energy?
38). Identify the compound with the lowest magnitude of lattice energy among the following:
KCl, KBr,SrO,CaO.
39). Identify the shortest bond.
A) single covalent bond
B) double covalent bond
C) triple covalent bond
D) all of the above bonds are the same length
40). Identify the weakest bond.
A) single covalent bond
B) double covalent bond
C) triple covalent bond
D) all of the above bonds are the same strength
41). Identify the number of bonding pairs and lone pairs of electrons in water.
A) 1 bonding pair and 1 lone pair
B) 1 bonding pair and 2 lone pairs
C) 2 bonding pairs and 2 lone pairs
D) 2 bonding pairs and 1 lone pair
E) 3 bonding pairs and 2 lone pairs
42) Write the best Lewis structure for OCl2.
43) Choose the best Lewis structure for ICl5.
A)
B)
C)
D)
E)
44) Choose the best Lewis structure for SF4.
A)
B)
C)
D)
E)
45). Choose the best Lewis structure for SeO4
2⁻.
A)
B)
C)
D)
E)
46). Which of the following processes are exothermic?
A) Cl2(g) → 2Cl(g)
B) Br(g) + e⁻ → Br⁻(g)
C) Li(s) → Li(g)
D) NaF(s) → Na⁺(g) + F⁻(g)
E) None of the above are exothermic.
47) Which of the following processes are exothermic?
A) the second ionization energy of Mg
B) the sublimation of Li
C) the breaking the bond of I2
D) the formation of NaBr from its constituent elements in their standard state
E) None of the above are exothermic
48). Use the bond energies provided to estimate ΔH°rxn for the reaction below.
PCl3(g) + Cl2(g) → PCl5(l) ΔH°rxn = ?
Bond Bond Energy (kJ/mol)
Cl-Cl 243
P-Cl 331
49) Use the bond energies provided to estimate ΔH°rxn for the reaction below.
2 Br2(l) + C2H2(g) → C2H2Br4(l) ΔH°rxn = ?
Bond Bond Energy (kJ/mol)
Br-Br 193
C≡C 837
C-C 347
C-Br 276
C-H 414
50) Use the bond energies provided to estimate ΔH°rxn for the reaction below.
CH3OH(l) + 2 O2(g) → CO2(g) + 2 H2O(g) ΔH°rxn = ?
Bond Bond Energy (kJ/mol)
C-H 414
C-O 360
C=O 799
O=O 498
O-H 464
51 ) Determine the electron geometry (eg) and molecular geometry (mg) of NCl3.
52) Determine the electron geometry (eg) and molecular geometry (mg) of BrF3.
53) Determine the electron geometry (eg) and molecular geometry (mg) of ICl2⁻.
54) Determine the electron geometry (eg) and molecular geometry (mg) of XeF2.
55) Consider the molecule below. Determine the molecular geometry at each of the 2 labeled
carbons.
56) Consider the molecule below. Determine the molecular geometry at each of the 3 labeled
atoms.
57). Determine the electron geometry (eg), molecular geometry (mg), and polarity of SO2.
58) Determine the electron geometry, molecular geometry and polarity of SF6 .
59) Describe a pi bond.
60) Which of the following best describes a sigma bond.
A) side by side overlap of p orbitals
B) end to end overlap of p orbitals
C) s orbital overlapping with the side of a p orbital
D) overlap of two s orbitals
E) p orbital overlapping with a d orbital
61) Fill in the black with the appropriate word. A molecule containing a central atom with sp
hybridization has a(n) __________ electron geometry.
62) How many electron groups around a molecule with sp hybridization.
63) Draw the Lewis structure for BrO4⁻. What is the hybridization on the Br atom?
64) Draw the Lewis structure for SF6. What is the hybridization on the S atom?
65) Draw the Lewis structure for BrF5. What is the hybridization on the Br atom?
66) How many of the following molecules have sp3 hybridization on the central atom?
XeCl4 CH4 SF4 C2H2
67). Use the molecular orbital diagram shown to determine which of the following is most stable.
68) Use the molecular orbital diagram shown to determine which of the following are
paramagnetic.
69) Use the molecular orbital diagram shown to determine which of the following are
paramagnetic.
70). Use molecular orbital theory calculate the bond order of N2 +
71). Use molecular orbital theory calculate the bond order of C2 –
72). Use molecular orbital theory calculate the bond order of O2 +
73). Based on molecular orbital theory which is more stable O2 or O2+
74). Based on molecular orbital theory which is more stable N2 or N2+
75). Based on molecular orbital theory which is more stable C2 or C2-
76). A Solution is prepared by dissolving 165 g of NaCl in 1000 ml of water. This solution was
labelled stock solution. Once the solution was prepared 200.00 ml sample of the solution was
transferred into a 500.ml volumetric flask and diluted to the mark with water. Following 125 ml
of this solution was transferred to a 200 ml volumetric flak and it was diluted to the mark with
water. What is the concentration of the last solution?
77). Imagine 100.0 ml of a 0.767 M of a sulfate solution was prepared by diluting 38.0 ml of a
stock solution to 100.ml with water. What is the concentration of the original solution?
78) Household hydrogen peroxide is an aqueous solution containing 3.0% hydrogen peroxide by
mass. What is the molarity of the solution? (assume density of the solution 1.01 g/mL.)
79). The Density of Nitric acid is 1.41 g/mL. Giving that Nitric Acid is 70.3%. by mass HNO3 in a
concentrated form that is 70.3% n
How much of the concentrated acid will be needed in order to make 1.15L of a 0.100M solution
of HNO3?
80) Which of the following reactions is associated with the lattice energy of Li2O (ΔH°latt)?
A) Li2O(s) → 2 Li⁺(g) + O2⁻(g)
B) 2 Li⁺(aq) + O2⁻(aq) → Li2O(s)
C) 2 Li⁺(g) + O2⁻(g) → Li2O(s)
D) Li2O(s) → 2 Li⁺(aq) + O2⁻(aq)
E) 2 Li(s) +
2
1
O2(g) → Li2O(s)
81) Which of the following reactions is associated with the lattice energy of CaS (ΔH°latt)?
A) Ca(s) + S(s) → CaS(s)
B) CaS(s) → Ca(s) + S(s)
C) Ca2⁺(aq) + S2⁻(aq) → CaS(s)
D) Ca2⁺(g) + S2⁻(g) → CaS(s)
E) CaS(s) → Ca2⁺(aq) + S2⁻(aq)
82) Which of the following reactions is associated with the lattice energy of RbI (ΔH°latt)?
A) Rb(s) +
2
1
I2(g) → RbI(s)
B) RbI(s) → Rb⁺(g) + I⁻(g)
C) RbI(s) → Rb(s) +
2
1
I2(g)
D) RbI(s) → Rb⁺(aq) + I⁻(aq)
E) Rb⁺(g) + I⁻(g) → RbI(s)
83) Identify the compound with the highest magnitude of lattice energy.
A) NaCl
B) KCl
C) LiCl
D) CsCl
84) Identify the compound with the lowest magnitude of lattice energy.
A) KCl
B) KBr
C) SrO
D) CaO
85) Place the following in order of decreasing magnitude of lattice energy.
K2O Rb2S Li2O
