Houston Community College System
Chemistry 1411
EXAM # 3A Sample
1
CHEM 1411 EXAM # 3
Name:______________________________
(Chapters 6 & 7)
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 .How many kJ of heat must be removed from 1.0x103 g of water (heat capacity of 4.184 J /g.K) to
lower the temperature from 18.0°C to 12.0°C?
A. 2.5x10-2 kJ
B. 1.4 kJ
C. 4.2 kJ
D. 25 kJ
_____ 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+
C. Al 3+
B. K
D. Na +
E. Mg
_____ 5. From the following heats of reaction,
2C (graphite) + H2 (g)  C2H2 (g)
∆ H = 227 kJ/mole
6C (graphite) + 3H2 (g)  C6H6 (l)
∆ H = 49 kJ/mole
calculate the heat for the reaction
3C2H2 (g)  C6H6 (l)
A. 632 kJ/mole
B. -632 kJ/mole
C. -178 kJ/mole
D. 178 kJ/mole
_____ 6. The heat of combustion of fructose, C6H12O6, is -2812 kJ. Using the following information,
f for fructose.
C6H12O6 (s) + 6 O2(g)  6 CO2(g) + 6 H2O (l)
∆ H°f ( CO2 ) = -393.5 KJ/mole
A -210.3 kJ/mol
∆ H°f (H2O) = - 285.83 KJ/mole
B. 210.3 kJ/mol
C. -1264 kJ/mol
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D. 1264 kJ/mol
_____ 7. What is the kinetic energy in J and cal of a 45-g golf ball moving at 61 m/s?
A. 168 J, 40 cal
B. 84 J, 20 cal
C. 84 J, 350 cal
D. 84 kJ, 20 kcal
_____ 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. Consider the combustion reaction of ethane gas, C2H6(g):
C2H6(g) + 7/2O2(g)  2CO2(g) + 3H2O(g) , ∆ H = -1430 kJ
What is the enthalpy change for the reverse reaction if whole number of coefficients are used?
A. +1430 kJ
B. -1430 kJ
C. -2860 kJ
_____ 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
D. +2860 kJ
E. none of these
_____11. Calculate the work for the expansion of CO2 from 1.0 to 4.7 liters against a pressure of 1.0 atm at
constant temperature.
A. 3.7 L·atm
B. 4.7 L·atm
C. 0 L·atm
D. –3.7 L·atm
E. –4.7 L·atm
____ 12. According to the first law of thermodynamics, the energy of the universe is constant. Does this
mean that
E is always equal to zero?
A. Yes, E = 0 at all times, which is why q = -w.
B. No, E does not always equal zero, but this is only due to factors like friction and heat.
C. No, E does not always equal zero because it refers to the system's internal energy, which is
affected by heat and work.
D. No, E never equals zero because work is always being done on the system or by the system
E. No, E never equals zero because energy is always flowing between the system and surroundings.
_____ 13. Arrange the following atoms in order of increasing atomic radius:
A. N < K < As < Fr
D. Fr < K < As < N
B. N < As < K < Fr
E. K < Fr < N < As
N, K, As, Fr
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
3, 2, 1, 0
D. 4, 3, 2, 1, 0
_____ 15. Consider the reaction:
When a 21.1-g sample of ethyl alcohol (molar mass = 46.07 g/mol) is burned, how much energy is
released as heat?
A. 0.458 kJ
B. 0.627kJ
C. 6.27  102 kJ
_____ 16. Which of the following has bond order of 3 ?
I. N2 II. CN- III) O2
A. I and II
B. I only
C. I,II, and IV
D. 2.89  104 kJ
E. 2.18kJ
IV) C22D. II and III
E. none of these
_____ 17. This fossil fuel was formed from the remains of plants that were buried and exposed to high
pressure and heat over time.
A. coal
B. natural gas
C. diesel fuel
D. propane
E. gasoline
_____ 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. The following statements concerning petroleum are all true except:
A. It is a thick, dark liquid composed mostly of hydrocarbons.
B. It must be separated into fractions (by boiling) in order to be used efficiently.
C. Some of the commercial uses of petroleum fractions include gasoline and kerosene.
D. It was probably formed from the remains of ancient marine organisms.
E. All of its hydrocarbon chains contain the same number of carbon atoms.
_____20. Which of the following does not have a standard enthalpy of formation equal to zero at 25°C and
1.0 atm?
A. F2(g)
equal to zero.
B. Al(s)
C. H2O(l)
D. H2(g) E. They all have a standard enthalpy
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Part (2) - Show all your work. ( 8 points each)
21. Calculate the work associated with the expansion of a gas from 42.0 L to 79.0 L at a constant pressure of
14.0 atm.
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.
24. . A 44.0 g sample of an unknown metal at 99.0 oC was placed in a constant-pressure calorimeter
of negligible heat capacity containing 80.0 mL water at 24.0 oC. The final temperature of the system
was found to be 28.4 oC. Calculate the Specific heat of the metal if density of water is 1.00 g/ml.
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:
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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?
CHEM 1411 EXAM # 3A (KEY)
1. D
11. D
16. C
2.q = m.s . ∆T = (1.0x103 g)(4.184 J/g.K)( 18.0 – 12.0 oC) = 25104 J = 25100 J /1000 = 25 kJ
7. B
K.E. = (mV2)/2 = (.045 kg )(61 m/s)2 / 2 = 84 J / 4.184 = 20 cal
12. C
17. A
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3. D ν = (c / λ ) = ( 3.00x108 m/s )/ 0.589x10-12 m ) = 5.09 x 1020 s-1 or Hz
8. B
13. B
18. C
4. B 9. D
For reverse reaction with whole number -2x (∆ H) = -2( -1430 kJ) = + 2860 kJ
14. D
19. E
5. B
Reaction I (3 x rev.)
3C2H2 (g)  6C (graphite) + 3H2 (g)
∆ H = 3(-227) kJ/mol
Reaction II (same)
6C (graphite) + 3H2 (g)  C6H6 (l)
∆ H = 49 kJ/mole
__________________________________________________________________________
Overall reaction
3C2H2 (g)  C6H6 (l)
∆ H = -632 kJ/mol
6. C
∆ H = ∆ H°f (reactants0 - ∆ H°f (products)
-2812 = [6(-285.83) + 6(-393.5)] – [ 6 (0) + ∆ H°f (fructose)] ∆ H°f (fructose)= -1264 kJ/mol
10. C
15. C
20. C
21. –518 L·atm
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.


C∆T (metal) = C ∆T (water)  ms ∆T (metal) = ms ∆T (water)
(44.0)(smetal) (99.0-28.4) = (80.0)(4.184)(28.4 -24)  smetal = 0.474 J/g.oC
25.
2s
 




2p
 


BONUS
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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)
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Houston Community College System
Chemistry 1411
EXAM # 3B Sample
CHEM 1411 EXAM # 3B
(6 & 7 )
Name: ________________________
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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. For a particular process q = - 17 kJ and w = 21 kJ. Which of the following statement is false?
A. Heat flows from the system to the surroundings
B. The system does work on the surroundings
C. ∆E = + 4 kJ
D. The process is exothermic
E. None of the above is false
_____ 2. Consider the reaction H2 (g) + (1/2) O2 (g) → H 2O (I) , ∆ H = - 286 kJ; which of the following is
true?
A. The reaction is exothermic
B. The reaction is endothermic
C. The enthalpy of the products is less than that of the reactants.
D. Heat is absorbed by the system
E. Both A and C are true
_____ 3. How much heat is required to raise the temperature of a 6.21 g sample of iron from 25.0 oC to 79.8 oC?
(specific heat of iron is 0.450 J /g . oC)
A. 70.0 J
B. 101 J
C. 386 J
D. 756 J
E. 153 J
_____ 4. Consider the following atoms and ions;which is(are) isoelectronic with Argon?
I. Cl-
II. Mg
A. only I
IV. K+
III. P
B. I and IV
C. Only IV
V. Ce
D. II,III, and V
E. none of these
____ 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. Which of the following is not being considered as an energy source for the future?
A. ethanol B. methanol C. seed oil D. shale oil
E. carbon dioxide
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_____ 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
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_____ 11. An element has the electron configuration [Kr] 5s 4d . The element is a(n):
A. non-metal
D. transition element
B. metalloid
E. two of these
(E) Bi
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. What is the specific heat capacity of silver if it requires 86.3 J to raise the temperature of 15 grams of
silver by 25°C?
A. 4.3 J/g°C
B. 0.23 J/g°C
C. 0.14 J/g°C
D. 0.60 J/g°C
E. none of these
_____ 14. What is true about the value of E?
A. It is greater than zero.
B. It is equal to zero.
C. It is less than zero.
D. More information is needed.
E. None of these
_____ 15. Which of the following statements correctly describes the signs of q and w for the following exothermic
process at P = 1 atm and T = 370 K?
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H2O(g)  H2O(l)
A. q and w are negative.
B. q is positive, w is negative.
C. q is negative, w is positive.
D. q and w are both positive.
E. q and w are both zero.
_____ 16. The change in enthalpy can always be thought of as equal to energy flow as heat.
A. true
B. false
C. sometimes D. depends on the temperature condition E. none of these
_____ 17. The H value for the reaction
when 66.9 g Hg is reacted with oxygen?
A. 0.333 kJ.
B. 6.07  103 kJ.
is -90.8 kJ. How much heat is released
C. 30.3 kJ
D. 90.8 kJ.
E. none of these.
_____ 18. Which of the following exhibits the correct orders for both atomic radius and ionization energy,
respectively? (smallest to largest)
A. S, O, F, and F, O, S.
B. F, S, O, and O, S, F.
C. S, F, O, and S, F, O.
D. F, O, S, and S, O, F.
E. None of these
_____ 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.
C) No change in energy occurs.
D) Light is emitted.
E) None of these.
Part (2) - Show all your work. ( 8 points each)
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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
Cl—Cl = 243
H—Cl = 431
N—Cl = 201
24. A 25.0 g piece of aluminum (which has a molar heat capacity of 24.03 J/ °C. mol) is heated 82.4 °C and
dropped into a calorimeter containing water (specific heat capacity of water is 4.18 J/ g . oC) initially at
22.3 °C. The final temperature of the water is 24.9 °C. Calculate the mass of water in the calorimeter.
25. Consider the following standard heats of formation:
P4O10(s) = -3110 kJ/mol
H2O(l) = -286 kJ/mol
H3PO4(s) = -1279 kJ/mol
Calculate the change in enthalpy for the following process:
P4O10(s) + 6H2O(l)  4H3PO4(s)
Bonus question (10 points). Please Show all your work for complete credit.
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Using Hess’s law of constant heat of summation and given:
I)
∆H = 44.1 kJ
H2O(l)  H2O(g)
II) CH3COCH3(l) + 4O2(g)  3CO2(g) + 3H2O(l)
∆H = 1787 kJ
III) CH3COOH(l) + 2O2(g)  2CO2(g) + 2H2O(l)
∆ H = 835 kJ
determine the enthalpy of reaction for
CH3COCH3 (l) + 2 O2(g)  CH3COOH(l) +CO2(g) + H2O(g)
CHEM 1411 EXAM # 3B (KEY)
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PART - I
1. C ( should be ΔE = +4 kJ)
4. B
7. E
10. A
13. B
16. B
19. D
2. E
5. D
8. A
11. E
14. B
17. C
20. B
o
o
o
3. E q = mc Δ T = (6.21 g)(0.450 J/g. C)(79.8 C –25.0 C) = 153 g
6. B largest wavelength has
smallest frequency
9. C ( l = 2 is d orbital with 10 electrons )
12.B
15. C
18. D
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
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. Δ Hrx = ΔHf 0 (products) - ΔHf 0 (reactants) = [ 4(-1279)] – [ (-3110) – (6(-286)]  Δ Hrx = -290 kJ
25. n ( mole C2H6 ) = (10.50 L)( 1 mol/22.4 L) = 0.469 mol
(0.468 mol C2H6) x ( 4 mole CO2 / 2 moles C2H6 ) = 0.938 mol CO2
V = nRT / P = ( 0.938)(0.0821)(300)(760) / 778  V = 22.6 L
Bonus Question
ΔH = ΔH (I) + ΔH (II) + reverse ΔH (III) = (-441.1 ) + (-1787) + +835) =  ΔH = -996 kJ
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