GENERAL CHEMISTRY I
EXAM 4
December 10, 2001
INSTRUCTIONS:
PRINT YOUR NAME ————>
NAME
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WORK 6 OF #1 THROUGH #8 (6 @ 25)
THREE PROBLEMS WILL BE DROPPED
SHOW YOUR WORK FOR PARTIAL CREDIT
USE THE CORRECT NUMBER OF SIGNIFICANT FIGURES
THE LAST TWO PAGES ARE A PERIODIC TABLE AND A SCRATCH SHEET
h = 6.626 X 10-34 J-s
c = 2.9979 X 108 m/s
J = (kg•m2)/s2
1
2
3
4
5
6
7
8
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TOTAL(150)
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1. Write the electronic configuration of the following ions. Note the same number of electrons as
the free atoms. You MAY use the short cut noble gas shortcut (such as [He] or [Ar]) for core
electrons.
(a) Cl(b) O 2(c) Sr2+
(d) Mn2+
(e) N3-
2. Arrange the three species in increasing order for the property given in the left column.
(a) 1st ionization energy
Cu
Ag
Au
_______ < ________ < ________
(b) atomic radii
P
Mg
Cl
_______ < ________ < ________
(c) radii
Cl –
Ca2+
S2–
_______ < ________ < ________
(d) ionization energy
O2+
O+
O
(e) radii
O2-
O
O+
(f) electronegativity
S
Si
Al _______ < ________ < ________
(g) radii
S
P
Cl
(h) electronegativity
Na
K
Li
(i) atomic
Cl
Br
F
(j) 1st ionization energy
Si
C
Ge _______ < ________ < ________
(k) radii
F
Cl-
Cl _______ < ________ < _______
radii
_______ < ________ < ________
_______ < ________ < ________
_______ < ________ < ________
_______ < ________ < ________
_______ < ________ < ________
3. Acetaminophen is the active ingredient in Tylenol and other over the counter medications. The
Lewis structure of Acetamionophen is below. Answer thre questions about the structure.
(a) How many sigma () bonds are in the molecule __________________
(b) How many pi () bonds are in the molecule ________________
(c) What is the hybridizations about the atoms that are indicated by the arrows?
Carbon(A)________
Carbon (B)
_______ Nitrogen (C)________
Carbon (D) ______ Oxygen(E) _______
(d) What are the approximate angles about the following atos? Do not rely on the figure to make
your answer. You must use VSEPR.
Carbon (A) _________ Carbon (b) __________ Oxygen (c) ___________
4. . Draw a valid Lewis structure and using VSEPR give the name of the shape of the following
molecules or ions Assign formal charges for (d) and (e).
(a) NF3
(b) XeCl4
(d) SO22C atom is central
(e) OCNC atom is central
(c) SOF4
S atom is central
(f) HNO3
N atom is central
Shape about the nitrogen
5. Draw three resonance structures for the ion NFSO- (The N atom is the central atom). Assign
formal charges to each of the. structures Determine which is the best structure of the three.
.Electronegativities N = 3.0, F= 4.0, S = 2.5, O = 3.5
6. Draw a valid Lewis structure for the following molecules or ions. Assign formal charges for
(b), and (e)
(a) FCN
Catom is central
(b) NO2-
(c) SF4
S atom is central
(d) H2CO
(e) CO3 2-
(f) BrF5
Br atom is central
7. The compound OF2 is unstable, giving oxygen and HF upon reaction with water:
F2O + H2O
2 HF + O2
Using the following bond energies, estimate the enthalpy of this reaction. You will need to draw
Lewis Structures. (Bond Energies in kJ O-F =192, OH = 463, H-F = 565, O=O = 498)
8. Draw a valid Lewis structure Determine whether the following molecules or ions are polar . A
table of electronegativities is at the end of the problem.
(a) CS2
(b) SO3
(c) ClF
(d)Cl2
(e) PCl3
(f) CH2F2
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Electronegativities of selected elements
H = 2.1,
Na = 0.9
C = 2.5
N = 3.0
O = 3.5
F = 4.0
Ti = 1.5
Si = 1.8
P = 2.1
S = 2.5
C l = 3.0