Houston Community College System
Chemistry 1411
EXAM # 3A Sample
1
CHEM 1411 EXAM # 3
Name:______________________________
(Chapters 7 & 8)
Score:
Directions- please answer the following multiple-choice questions next to each number. Please show all your
work for bonus question and part(2) questions in the space provided.
Part (1) - Multiple Choice - (3 points each)
_____ 1. How many unpaired electrons are in the Lewis dot symbol of a chlorine atom?
A. 7
B. 3
C. 5
D. 1
E. 8
_____ 2. Which of the following molecules consider to be a polar molecule?
A. NH3
B. BF3
C. CO2
D. C2H2
E. CCl4
_____ 3. What is the frequency of radiation that has a wavelength of 0.589 pm?
A. 1.96 x 10-21 s-1
B. 5.09 s-1
C. 5.09 x 108 s-1
D. 5.09 x 1020 s-1
_____ 4. Which one has the largest radius ?
A. K+
B. K
C. Al 3+
D. Na +
E. Mg
_____ 5. Which one is isoelectronic with Neon ?
A. F-
B. Al3+
C. Na +
D. O2-
E. all of these
_____ 6. Which one violates octet rule stability ?
A. S2-
B. Mg+
C. O2-
D. Fr+
E. Al 3+
_____ 7. Which one of the following forms an ionic bond with Chlorine gas?
A. C
B. Mg
C. P
D. As
E. S
_____ 8. Statement, electrons fill the orbital singlet, then double up is called………….
A. Aufba principle
C. Puali's exclusion principle
B. Hund's rule
D. none of these
_____ 9. Which of the following molecules is exception to octet rule.
A. PCl5
B. COCl2
C. BCl3
D. CCl4
_____ 10. Which of the following is the electron configuration for the Cr3+ ?
A. [Ar] 4s2 3d4 B. [Ar] 4s1 3d5 C. [Ar] 3d3
D. [Ar] 4s2 3d1
E. two of these
E. none of these
_____11. As the bond order of a bond increases, the bond energy ________and the bond length __________.
2
A. increase, increase
D. decrease, increase
B. decrease, decrease
C. increase, decrease
E. More information is needed to answer this question
____ 12. How many valence electron are in SO42- ion?
A. 32eB. 30eC. 14eD 28eE. 24e_____ 13. Arrange the following atoms in order of increasing atomic radius: N, K, As, Fr
A. N < K < As < Fr
D. Fr < K < As < N
B. N < As < K < Fr
E. K < Fr < N < As
C. As < K < N < Fr
_____ 14. For n = 4, what are the possible values of l?
A. 3, 2, 1
B. 4, 3, 2, 1
C.
3, 2, 1, 0
D. 4, 3, 2, 1, 0
_____ 15. The electron-pair geometry and molecular geometry of boron trichloride are respectively
A. tetrahedral,tetrahedral
B. tetrahedral, trigonal planar
C. trigonal planar, trigonal planar
D. tetrahedral, trigonal pyramidal
E. tetrahedral, trigonal bipyramidal
_____ 16. Which of the following has bond order of 3 ?
I. N2 II. CN- III) O2
A. I and II
B. I only
IV) C22-
C. I,II, and IV
D. II and III
E. none of these
_____ 17. Which of the following groups contains no ionic compounds?
A. HCN, NO2, Ca(NO3)2
D. KOH, CaF2, NaNH2
B. PCl5, LiBr, Zn(OH)2
E. CH2O, H2S, NH3
C. NaH, CCl4, SF4
_____ 18. Write the electron configuration for the atom Cu, using the appropriate noble-gas inner core for
abbreviation.
A. [Ar]4s23d10
B. [Ar]4s24d9
C. [Ar]4s13d10
D. [Kr]4s13d10
_____ 19. Which of the following is not a valid resonance structure for N3¯ ?
N = N - N:
I.
A. I only
:N
N - N:
II.
B. II only
:N-N
N:
N=N=N
III.
C. I and II
D. II and IV
IV.
E. all are correct
_____20. Consider the following atoms and ions;which is(are) isoelectronic with Argon?
I. ClA. only I
II. Mg
III. P
B. I and IV
IV. K+
C. Only IV
of these
3
V. Ce
D. II,III, and V
E.
none
Part (2) - Show all your work. ( 8 points each)
21. Calculate the enthalpy change, H , for the following gasphase reaction using bond energy data.
Dissociation energy
H
H
\

C=C + H-Cl
 \
H
H
H H
 
 H-C-C-H
 
H Cl
H-Cl
C-H
C-C
C=C
C-Cl
435KJ/mol
413 KJ/mol
348 KJ/mol
614 KJ/mol
328 KJ/mol
22. For the electronic transition from n = 3 to n = 5 in the hydrogen atom, calculate the energy,
and wavelength (in nm).
23. Write electron and core configuration for Bromine atom and determine the total number of unpaired
electrons.
4
24. Write the ground state electron configurations (or core configurations) for the followings and
determine the
total number of unpaired electrons and magnetic properties (paramagnetic or diamagnetic) in each.
a) Chromium (Cr) __________________________________________ ,________, _________
b) Zinc (Zn)
___________________________________________,________, _________
25. Nitrogen has how many valence electrons? Fill in the orbitals with the correct electron arrangements &
energy levels.





BONUS question-Show all your work.(10 points)
Photogray lenses incorporate small amounts of silver chloride in the glass of the lens. The following reaction
occurs in the light, causing the lenses to darken:
AgCl  Ag + Cl
The enthalpy change for this reaction is 3.10  102 kJ/mol. Assuming all this energy is supplied by light,
what is the maximum wavelength of light that can cause this reaction?
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CHEM 1411 EXAM # 3A (KEY)
1. D
2. A
3. D
6. B
11.
7. B
12. A
ν = (c / λ ) = ( 3.00x108 m/s )/ 0.589x10-12 m ) = 5.09 x 1020 s-1 or
13. B
18. C
9. E
14. D
10. C
15. C
4. B
5. E
21. H = [ 614 + 435 ] - [ 328 + 348 + 413 ] =
16. C
17. E
8. B
19. A
20. B
-40 KJ
22.  E = 2.18 x 10 18 ( 1/32 - 1/52 ) = 1.55 x 10 19 J
 E = hc/
( 6.63 x 10 34 )( 3.00 x 108 )
 = ------------------------------------------ = 1.28 x 106 m = 1280 nm
( 1.55 x 10 19 )
23. 35Br = 1ss 2s2 2p6 3s2 3p6 4ss 3d10 4p5 = [ Ar ] 4ss 3d10 4p5
One unpaired electron

24.


Cr : [Ar] 4s1 3d5 , 6 unpaired electrons , paramagnetic
Zn :[Ar] 4s2 3d10 , 0 unpaired electrons, diamagnetic
25.
2s
 




2p
 


BONUS
Enthalpy change per AgCl = (3.10  102 kJ/mol)(1 mol/6.022  1023 molecules)(1000 J/1kJ) = 5.15  10–19
J/molecule
E = hc/, therefore  = hc/E
l = (6.626  10–34 J s)(2.998  108 m/s) / (5.15  10–19 J) = 3.86  10–7 m (or 386 nm)
6
Houston Community College System
Chemistry 1411
EXAM # 3B Sample
7
CHEM 1411 EXAM # 3B
(7 & 8 )
Name: ________________________
Score:
Directions- please answer the following multiple-choice questions next to each number. Please
show all your work for bonus question and part (2) questions in the space provided.
Part (1) - Multiple Choice - (3 points each)
_____ 1.Which molecule contains one unshared pair of valence electrons?
(A) H2O
(B) NH3
(C) CH4
(D) NaCl
(E) CO2
_____ 2. In the Lewis structure of SF2, there are ____ single bonds and ____ total lone pairs?
(A) 2,8
(B) 3,8
(C) 2,2
(D) 2,6
(E) 3,6
_____ 3. Which of the following molecules violates the octet rule?
(A) CBr4
(B) NF3
(C) OF2
(D) PCl3
(E) AsF5
(D) H2Se
(E) NF3
_____ 4. Which molecule exhibits resonance?
(A) O3
(B) BeCl2
(C) CO2
____ 5. Which of the following quantum number combinations is incorrect for an orbital designation?
A. n = 2 , l = 0
C. n = 2 , l = 1 , m = -1
E. All incorrect
B. n = 1 , l = 0 , m = 0
D. n = 2 , l = 0 , m = -1 , s = + ½
_____6. Which of the following frequencies corresponds to light with the longest wavelength?
A. 3.00 × 1013 s-1
B. 4.12 × 105s-1
C. 8.50 × 1020 s-1 D. 9.12 × 1012 s-1
E. 3.20 × 109 s-1
_____ 7. What are the formal charges on the boron and nitrogen in the compound BF3-NH3?
(B) +2 and –2
(E) -1 and +1
(A) -2 and +2
(D) +1 and –1
(C) 0 and 0
_____ 8. Which would be expected to be the most electronegative?
(A) P
(B) As
(C) Si
(D) Al
_____ 9. How many electrons in an atom can have the quantum numbers n=3, l=2?
A. 2
B. 5
C. 10
D. 18
E. 6
_____ 10. The element with the greatest tendency to gain electrons is
(A) F
(B) At
(C) O
(D) N
2
10
_____ 11. An element has the electron configuration [Kr] 5s 4d . The element is a(n):
8
(E) Bi
A. non-metal
D. transition element
B. metalloid
E. two of these
C. metal
_____ 12. How many of the following electron configurations for the species in their ground state are
correct?
i. Ca: 1s22s22p63s23p64s2
ii. Mg: 1s22s22p63s1
iii. V: [Ar] 3s23d3
iv. As: [Ar] 4s23d104p3
v. P: 1s22s22p63p5
A. 1
B. 2
C. 3
D. 4
E. 5
_____ 13. Which of the following compounds contains the LEAST polar bonds?
Atoms
H
S
P
As
Cl
Si
Electronegativity 2.1 2.5
2.1
2.1
3.0
1.8
(A) PH3
(B) AsCl3
(C) SiH4
_____ 14. Which pair is geometrically similar?
(A) SO2 and CO2
(B) CO2 and OF2
Sb
1.9
(D) SbCl3
(C) PH3 and BF3
(E) H2S
(D) SO2 and O3
_____ 15. A molecule consists of four bonding pairs of electrons and no lone pairs. What is its structure?
(A) square planar
(B) tetrahedral
(C) linear
(D) square pyramidal
_____ 16. Which of the following species is paramagnetic?
(A) O2 only
(B) N2 only
(C) N2 and B2
(D) N2 and O2
(E) B2 and O2
_____ 17. Predict the real bond angles in SeCl2 using the VSEPR theory:
(A) more than 120°
(B) between 109 and 120
(C) between 90 and 109
(D) 90
_____ 18. The lattice energy for ionic crystals increases as the charge on the ions ___ and the size of the ions ___?
(A) increases, increases
(C) decreases, increases
(B) increases, decreases
(D) decreases, decreases
_____ 19. The four lines observed in the visible emission spectrum of hydrogen tell us that:
A) The hydrogen molecules they came from have the formula H4.
B) We could observe more lines if we had a stronger prism.
C) There are four electrons in an excited hydrogen atom.
D) Only certain energies are allowed for the electron in a hydrogen atom.
_____ 20. In Bohr's atomic theory, when an electron moves from one energy level to another energy level more
distant from the nucleus:
A) Energy is emitted.
B) Energy is absorbed.
9
C) No change in energy occurs.
D) Light is emitted.
E) None of these.
Part (2) - Show all your work. ( 8 points each)
21. Calculate the wavelength and frequency of light that is emitted when an excited electron in the hydrogen atom
falls from n=5 to n=2?
22.Write the equations correctly represents the process involved in the electron affinity of X?
23. Calculate the enthalpy change, H, for the following reaction using bond dissociation energy data.
Bond dissociation energies, given in kJ/mole:
NH3(g) + Cl2(g)  NH2Cl(g) + HCl(g)
N—H = 389
a)
b)
c)
Cl—Cl = 243
H—Cl = 431
24. For each of the following compounds:
Draw the Lewis structure.
Give the shape of the molecule.
Indicate the polarity of the molecule.
AlF3, ICl4–
10
N—Cl = 201
Bonus question (10 points). Please Show all your work for complete credit.
Calculate the lattice energy for LiCl(s) given the following:
sublimation energy for Li(s)
Hf for Cl(g)
first ionization energy of Li(g)
electron affinity of Cl(g)
enthalpy of formation of LiCl(s)
+166 kJ/mol
+119 kJ/mol
+520. kJ/mol
–349 kJ/mol
–409 kJ/mol
CHEM 1411 EXAM # 3B (KEY)
PART - I
1. B
2. A
3. E
electrons )
4. A
7. E
10. A
13. A
5. D
8. A
11. E
14. D
6. B largest wavelength has smallest frequency
12.B
15. B
18. B
16. E
19. D
17. C
20. B
9. C ( l = 2 is d orbital with 10
PART - II
21. hc/λ = 2.18x10 –18( 1/ni2 – 1/nf2)  (6.63x10 –34)(3.00x108) /λ = 2.18x10 –18( 1/52 – 1/22)  λ = 4.34x10 –7 m
h ν = 2.18x10 –18( 1/ni2 – 1/nf2)  (6.63x10 –34) ν = 2.18x10 –18( 1/52 – 1/22)  ν = 6.91 x1014 sec -1
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22. X(g) + e- => X-(g)
23. H = [ D (N-H) + D(Cl- Cl))]  [ D ( N - Cl) + D (H – Cl) ] =
[ (389 + 243) – (201 + 431) = ( 632)  9632) = 0 kJ
24. Part A:
Part B: trigonal planar
Part C: nonpolar
Part A:
Part B: square planar
Part C: nonpolar
Bonus Question
–865 kJ/mol
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