Final Examination
Chemistry 1412
1
Final Exam 1412
PART I (2 points each)
Multiple choice - Please DO NOT write or mark on this paper. Write your correct answer on scantron.
1. . In the reaction 2H2O2(aq) → 2H2O(l) + O2(g), the initial concentration of H2O2 is 0.557 M and, 20.4 s
later, the concentration of H2O2 is 0.311 M. What is the initial rate of the reaction?
a. 0.0121 M/s
2.
b. 0.00403 M/s
c. –0.0121 M/s
d. 0.00603 M/s
A red blood cell placed in pure water will swell because?
A) the osmotic pressure is greater in the water than in the cell.
B) the osmotic pressure is greater in the cell than in the water.
C) the osmotic pressure is the same in the cell and the water.
D) water moves from a higher osmotic pressure to a lower osmotic pressure.
E) the vapor pressure of the water in the cell is greater than the vapor pressure of
pure water.
3. value of Kp for the reaction 2NO2(g)  N2O4(g) is 1.52 at 319 K. What is the value of Kp at this
temperature for the reaction
N2O4(g)  2NO2(g)?
a. -1.52
b. 1.23
c. 5.74 x 10-4
d. 0.658
4. For which of the following reactions is Kc equal to Kp?
a. N2O4(g)  2NO2(g)
c. H2(g) + Cl2(g)  2HCl(g)
b.
d.
2SO3(g)  2SO2(g) + O2(g)
C(s) + CO2(g)  2CO(g)
5. What is the molality of a solution prepared by dissolving 0.148 mol of chloroform, CHCl 3, in 428 g of
toluene, C6H5CH3?
A)
B)
C)
D)
E)
0.346 m
0.0318 m
0.0415 m
0.0308 m
0.633 m
6. For first-order reactions the rate constant, k, has the units
A. M s-1
7.
B. M-1 s-1
C. M-2 s-1
D. s-1
Which of the following is not a colligative property?
2
A)
B)
C)
D)
osmotic pressure
vapor pressure lowering
freezing-point depression
lattice energy
8. .It is safe to make the simplifying assumption that x can be neglected in the denominator of the
equilibrium equation when
Ka
 100 .
C
A. a
B. K a  Ca .
Ca
 100 .
Ka
C.
D.
Ca
 100
Ka
9. Rank acetic acid (HC2H3O2), hydrocyanic acid (HOCN), and hydrofluoric acid (HF) in order of
increasing strength.
Acid
Ka
HC2H3O2 1.8 × 10-5
HOCN
3.5 × 10-4
HF
6.8 × 10-4
A.
C.
HC2H3O2 < HOCN < HF B.
HF < HOCN < HC2H3O2 D.
HOCN < HC2H3O2 < HF
HF < HC2H3O2 < HOCN
10. If the reaction 2A + 3D  products is first-order in A and second- order in D,
then the rate law will have the form rate =
a. k[A]2[D]3
b. k[A][D]
c. k[A]2[D]2
d. k[A][D]2
11. For the elementary reaction NO3 + CO  NO2 + CO2
a.
the molecularity is 2 and rate = k[NO3][CO]/[NO2][CO2]
b.
the molecularity is 4 and rate = k[NO3][CO]/[NO3][CO]
c.
the molecularity is 4 and rate = k[NO3][CO][NO2][CO2]
d.
the molecularity is 2 and rate = k[NO3][CO]
12. For the system CaO(s) + CO2(g)  CaCO3(s) the equilibrium constant expression for Keq is
A.
[CO2]
B. 1 / [CO2]
C.
[CaO] [CO2] / [CaCO3]
D.
[CaCO3] / [CaO] [CO2]
13. Which of the following equilibria best represents the hydrolysis reaction that occurs in an aqueous
solution of NH4Cl?
A. NH4+(aq) + Cl–(aq)
B. Cl–(aq) + H2O(l)
C. NH4+(aq) + OH–(aq)
D. NH4+(aq) + H2O(l)
NH4Cl(s)
HCl(aq) + OH–(aq)
NH3(aq) + H2O(l)
NH3(aq) + H3O+(aq)
14. Which of the following acids has the weakest conjugate base?
3
A HF
B. HI
C. CH3COOH
D. HNO2
15. At normal body temperature, 37°C, Kw = 2.4 x 10-14.
Calculate [H+] if [OH-] = 1.3 x 10-9 M at this temperature.
A. 1.3 x 10-9 M
B. 1.0 x 10-7 M
C.7.7 x 10-6 M
D. 1.9 x 10-5 M
16. If Ka for HCN is 6.2x10-10, what is Kb for CN- ?
A. 6.2x10-24
B. 6.2x104
C. 1.6x10-5
D. 1.6x1023
17. What is the solubility product expression for Au(OH)3?
A. Ksp = [Au3+][OH–]
B. Ksp = [Au3+][OH–]3 C. Ksp = [Au3+][3OH–] D. Ksp = [Au3+][3OH–]3
18. For the isothermal (constant-temperature) expansion of an ideal gas,
A. w > 0 and q > 0.
B. w < 0 and q > 0.
C. w > 0 and q < 0. D. w = 0 and q > 0.
19 What is ∆G° at 298 K for the following equilibrium?
Ag+(aq) + 2NH3(aq)
Ag(NH3)2+(aq); Kf = 1.7 × 107 at 298 K
A. –41 Kj
B. 41 kJ
C. –18 kJ
D. 18 kJ
20. For the reaction 4Ag(s) + O2(g) → 2Ag2O(s), ∆H° = –61.14 kJ and ∆S° = –132 J/K at 25°C. Which of
the following statements is true? Assume that ∆H° and ∆S° are essentially temperature
independent.
A.
B.
C.
D.
The reaction will be spontaneous at all temperatures.
The reaction will not be spontaneous at any temperature.
The reaction will be spontaneous at low temperatures, and the reverse reaction will be
spontaneous at high temperatures.
The reaction will be spontaneous at high temperatures, and the reverse reaction will be
spontaneous at low temperatures.
21. For which of the following reactions is ∆S° at 25°C closest to zero?
A. H2(g) + I2(s) → 2HI(g)
B. C2H4(g) + Br2(l) → C2H4Br2(l)
C. N2(g) + O2(g) → 2NO(g)
D. 2NO(g) + O2(g) → 2NO2(g)
22. Which of the following represents a spontaneous reaction ?
A. K < 1
D. all of these
4
23. What is the thermodynamic quantity that provides the criterion for the spontaneity of a chemical
reaction?
A. ∆S
B. ∆H
C. ∆U
D. ∆G
24. ∆H and ∆U are nearly the same in all the following processes except
A. F2(g) + H2(g) → 2HF(g).
C. CuO(s) + H2(g) → Cu(s) + H2O(g).
B. 3O2(g) → 2O3(g).
D. CH4(g) + Cl2(g) → CH3Cl(g) + HCl(g).
25. Which of the following is true for the cell shown here?
Zn(s)  Zn2+(aq)  Cr3+(aq)  Cr(s)
A) the electrons flow from cathode to the anode
B. the electrons flow from the zinc to the chromium
C) the electrons flow from the chromium to the zinc
D) the zinc is reduced
26. The standard reduction potentials for the following half reactions are given as follows;
Cr3+ + 3e‾  Cr(s)
Br2(aq) + 2e‾  2Br-
E0 = -0.73 V
E0 = +1.09 V
what is the E0 for this cell?
A) 1.82 V
B) 0.36 V
C) 4.75 V
D) 1.79 V
27. . Which of the following represents positron?
A) 11 H
B) 0-1 e
C) 0+1 e
D) 42 He
28. Which of the following statements is true?
A)
B)
C)
D)
As a radioactive isotope decays, its half-life remains the same and its rate of disintegration
remains the same.
As a radioactive isotope decays, its half-life remains the same and its rate of disintegration
increases over time.
As a radioactive isotope decays, its half-life remains the same and its rate of disintegration
decreases over time.
As a radioactive isotope decays, its half-life decreases over time and its rate of disintegration
remains the same.
29. . According to the following cell notation, which species is undergoing oxidation?
5
Cu | Cu2+(aq) || Mn2+(aq) | MnO2(s) | Pt
A)
Cu
B)
Cu2+
C)
Pt
D)
MnO2
30. Which of the following balanced equation is labeled incorrectly?
A. Beta decay,
23992
U 
23993
Np + 0-1 e
B. Alpha Bombardment, 2411 Na + 42 He 
C. Electron capture,
7
4
Be + 0-1e 
7
3
2713
Al +10 n
Li
D. All are correctly labeled
31. Acetylene, C2H2, the simplest alkyne, can be prepared from "inorganic" materials. Which of
these reactions is used to prepare acetylene in this way?
A)
B)
2C + H2 → C2H2
C2H4 →C2H2 + H2
C)
D)
2CO + 2H2O → C2H2 + H2O2
CaC2 + 2H2O → C2H2 + Ca(OH)2
32. What is the abbreviated notation for the following nuclear bombardment reaction?
27
4
30
1
13 Al + 2 He → 15 P  0 n
A)
27
13
Al  ,   30
15 P
B)
27
13
Al  n,   30
15 P
C)
27
13
Al  , n  30
15 P
D)
27
13
Al  n, d  30
15 P
33. A scintillation counter measures radiation by detecting
A)
B)
C)
D)
electrons released when gas atoms are ionized by the radiation.
alpha and beta particles as they strike a detector window.
flashes of light emitted from a phosphor affected by radiation.
the increase in temperature when a gas is struck by radiation
34 Warfarin is used to prevent blood clots from forming or growing larger in your blood
and blood vessels. How many different functional groups are in Warfarin?
A) 3
B) 4
C) 5
6
D) 6
35. A particular structural isomer of C6H14 is shown below.
Which of the following structures represents a different structural isomer of C6H14 than
the one shown above?
A) A
B) B
Part II-( 5 points each)
C) C
D) D
Name: _______________________
Show work- Please write your complete work on scantron.
Partial credit will be given.
1. The rate constant for a particular reaction is 2.7 x 10-2 s-1 at 25°C and 6.2 x 10-2 s-1 at 75°C. What is the
activation energy for the reaction in kJ/mol? ( R = 8.314 J/mol.K)
7
2. Initial rate data were obtained for the following reaction:
A(g) + 2B(g)  C(g) + D(g)
initial
Experiment
1
2
3
initial
initial
[A], mol/L [B], mol/L
0.15
0.30
0.15
0.10
0.10
0.20
rate ,Ms-1
0.45
1.8
0.9
What are the rate law and k value for the reaction?
3. Give the proper IUPAC names or structures for the followings:
I)
____________________________
H3C
II)
Cl
C=C
H
H
III) 1,3-dimethylcyclopentane
____________________________
____________________________
IV) 1-chloro-2,2-dimethylpentane
____________________________
4. A 50.0-mL sample of 0.50 M acetic acid, CH3COOH, is titrated with a 0.150 M NaOH solution.
Calculate the pH after 25.0 mL of the base have been added (Ka = 1.8 x 10−5).
8
5. . Determine ∆G° for the following reaction:
CH4 ( g )  2O2 ( g )  CO2 ( g )  2H 2O(l )
Substance
CH4(g)
O2(g)
CO2(g)
H2O(l)
6. The isotope
∆Gf° (kJ/mol)
–50.67
0
–394.4
–237.4
210Pb
has a half-life of 22 years. What percentage of a pure 210Pb sample prepared
in April 1937 remains in April 2001?
7. What mass of chromium could be deposited by electrolysis of an aqueous solution of Cr2(SO4)3 for 175
min using a constant current of 13.0 A? (F = 96485 C/mol)
8. Cr3+(aq) + 3e–
Pb2+(aq) + 2e–
Cr(s); E° = –0.74 V
Pb(s); E° = –0.13 V
What is the standard Gibbs free-energy change for the following reaction?
2Cr(s) + 3Pb2+(aq) → 3Pb(s) + 2Cr3+(aq)
9
CHEMISTRY FINAL CHEM 1412 EXAM(answers)
Part I -Multiple Choice Questions (2 points each)
1. D
2. b
3. D
4. C
5. a
6. A
8. D
9. A
10. D
11. D
12. B
13. D
15. D
16. C
17. B
18. B
19. A
20. C
22. B
23. D
24.B
25. B
26. A
27. C
29. A
30. D
31. d
32. C
33. A
34. C
Part II – Show work
1. ln(k1/k2) = -(Ea/R)(1/T1 –1/T2)  ln (2.7x10-2/6.2x10-2) = -(Ea/8.314)(1/298
7. d
14. B
21. C
28. C
35. c
– 1/348)
 -0.8313 = -Ea (0.000058)  Ea = 14332.716 J/mol (divided by 1000)  Ea = 14 kJ/mol
2. EXP 1 & 2: Concentration of A is doubled, concentration of B is kept constant, initial rate increases
by a factor of 4. That means that the reaction is second order in A.
EXP 1 & 3: Concentration of A is kept constant, concentration of B is doubled, initial rate increases
by a factor of 2. That means that the reaction is first order in B. Rate = k [A] 2[B]
EXP 1: 0.45 Ms-1 = k (0.15M)2(0.10M)  k = 200 M-2s-1
3.
I) 3-methyl -1-pentene
II)
cis-1- chloro-1-propene
III)
IV)
CH3
CH3
CH3 - CH2 - CH2 - C - CH2 - Cl
CH3
CH3
4.
(0.50)(50.0)
+
[ H ] = Ma =
= 0.33 M(MORE ACIDIC), pKa = 4.75
(50.0 + 25.0)
(0.150) (25.0)
-
[OH ] = Mb =
= 0.05 M
(50.0 + 25.0)
Mb
pH =4.75 +log
Ma - Mb
5.
6.
0.05
= 4.75 + log
= 4.75 - 0.748 = 4.00
0.33 - 0.05
-818.5 KJ
13% (#62 20.4)
7. 24.5 g
8. -353KJ
10
11
Houston Community College System
Departmental
SAMPLE
Final Examination
Chemistry 1412B
Cortisone (steroid)- reduces swelling and decreases the body's immune response
Final Sample Exam 1412B
PART I (2 points each)
Multiple choice - Please DO NOT write or mark on this paper. Write your correct answer
on scantron.
1. In the reaction, HSO4- + HS- ↔ H2S + SO42- , which one of the sets below constitutes a conjugate (acidbase) pair?
12
A) HSO4-, HS-
B) HSO4- , H2S
C) H2S , HS-
D) HS-, SO42-
C) AgNO3
D) NaC2H3O2
2. Which one of the species below is insoluble in water?
A) ZnSO4
B) PbCrO4
3. A glucose solution is prepared by dissolving 5.10 g of glucose, C6H12O6, in 110.5 g of water. What is the
molality of the glucose solution?
A) 0.283 m
B) 0.000256 m
C) 0.245 m
D) 0.256 m
4. What is the expected freezing point of a solution that contains 25.0g of fructose, C6H12O6, in 250.0g of
water? Ki = 1.86 °C m-1
A) -0.10°C
B) +0.10°C
C) -1.03°C
D) +1.86°C
5. Which of the following reactions accompanied by an increase in entropy?
A) ZnS(s) + 3/2 O2(g) → ZnO(s) + SO2(g)
C) BaO(s) + CO2(g) → BaCO3(s)
B) CH4(g) + H2O(g) → CO(g) + 3H2(g)
D) Na2CO3(s) + CO2(g) + H2O(g) → 2 NaHCO3(s)
6. The nuclear particle which is described by the representation, 11 X, is called:
A) alpha particle
B) electron
C) neutron
D) proton
7. Butene, C4H8, is a hydrocarbon with one bond. How many noncyclic isomers can be drawn?
A) 1
B) 2
C) 3
D) 4
8. If the OH- ion concentration in an aqueous solution at 25.0 oC is measured as 3.4 x 10-3 M, then the pH is?
A) 2.47
B) 7.22
C) 8.24
D) 11.53
9. A galvanic cell has two electrodes. Which statement below is correct?
A)
B)
C)
D)
Reduction takes place at the anode, which is positively charged.
Reduction takes place at the anode, which is negatively charged.
Reduction takes place at the cathode, which is positively charged.
Reduction takes place at the cathode, which is negatively charged.
10. If a reaction involves a single reactant is first order with a rate constant of 4.50× 10-2 s-1, how much
time is required for 75.0% of the initial quantity of reactant to be used up?
A) 16.7 seconds
B) 30.8 seconds
C) 23.1 seconds
D) 25.3 seconds
11. For the reaction, 2XO + O2  2 XO2, some data obtained from measurements of the initial rate of
reaction at varying concentrations is given below.
Run #
1
2
[XO]
0.010
0.010
[O2]
0.010
0.020
13
rate, mmol L-1 s-1
2.5
5.0
3
0.030
0.020
45.0
The rate law is therefore:
A) rate = k[XO]2 [O2]
C) rate = k[XO] [O2]2
B) rate = k[XO] [O2]
D) rate = k[XO]2 [O2]2
12. Which one of the following is the strongest acid?
A) HClO (Ka = 3.0 x 10-8)
C) HNO2 (Ka = 4.5 x 10-4)
B) HF (Ka = 6.8 x 10-4)
D) HCN (Ka = 4.9 x 10-10)
13. Using the standard entropy values:
H2(g), So = + 130.6 J mol-1 K-1 I2(s), So = + 116.12 J mol-1 K-1
Calculate the standard entropy change, ∆So, for the reaction:
A) -40.8 J
B) +40.8 J
HI(g), So = + 206.5 J mol-1 K-1
H2(g) + I2(g) → 2 HI(g)
C) -165.3 J
D) +165.3 J
14. Consider the following reaction at equilibrium:
H = + 92.4 kJ
2NH3(g)  N2(g) + 3H2(g)
Adding H2(g) to the system at equilibrium will ____________________
A) decrease the concentration of NH3(g) at equilibrium
B) remove all of the N2(g)
C) increase the value of the equilibrium constant
D) decrease the concentration of N2(g) at equilibrium
15. The equilibrium constant for the reaction, H2(g) + I2(g) ↔ 2 HI(g) is 54.9 at 699.0 K. What is the
equilibrium constant for 4 HI(g) ↔ 2 H2(g) + 2 I2(g) under the same condition?
A) 109.8
B) 9.11 x 10-3
C) 3.32 x 10-4
D) -109.8
16. A 0.400 M solution of an acid, HA, has a pH = 1.301. What is the value of the ionization constant, Ka, for
this acid?
A) 5.00 x 10-2
B) 1.25 x 10-3
C) 5.56 x 10-3
D) 6.25 x 10-3
17. What is the balanced form of the following unbalanced redox equation that takes place in an
acidic medium?
NO2-(aq) + Cr2O72-(aq)  Cr3+(aq) + NO3-(aq)
A) NO2-(aq) + Cr2O72-(aq) + 8H+(aq)  2Cr3+(aq) + NO3-(aq) + 4H2O(l)
B) 3NO2-(aq) + Cr2O72-(aq)  2Cr3+(aq) + 3NO3-(aq) + 4H2O(l)
C) 3NO2-(aq) + Cr2O72-(aq) + 8H+(aq)  2Cr3+(aq) + 3NO3-(aq) + 4H2O(l)
D) 3NO2-(aq) + Cr2O72-(aq) + 16H+(aq)  2Cr3+(aq) + 3NO3-(aq) + 8H2O(l)
18. A buffer solution is prepared by taking 0.250 moles of acetic acid ( pKa = 4.74) and 0.400 moles of sodium
14
acetate in sufficient water to make 1.800 liters of solution . Calculate the pH.
A) 4.95
B) 4.66
C) 4.86
D) 4.56
19. Oxidation refers to ______ electrons, reduction refers to ________ of electrons.
A) Gain; gain
B) Loss; gain
C) Neutralization; loss
D) Gain; loss
20. 40.0 ml of 0.10 M HCl(aq) was added to 50.0 ml of 0.10 M NaOH(aq) and the mixture was stirred, then
tested with a pH meter. What pH should be obtained at 25.0 oC?
A) 1.95
B) 12.05
C) 7.00
D) 12.50
21. What element undergoes alpha decay to form lead-208 ( Pb)?
82
222
A)
131
Radon (Rn)
B)
86
84
C)
Xenon(Xe)
54
212
Krypton (Kr)
36
D)
Polonium (Po)
84
22. The solubility of silver oxalate, Ag2C2O4, in pure water is 2.06 x 10-4 moles per liter. Calculate the value of
Ksp for silver oxalate from this data.
A) 4.24 x 10-8
B) 8.49 x 10-8
C) 1.75 x 10-11
D) 3.50 x 10-11
23. Hydrocarbons containing a carbon-carbon triple bond are called _____________ .
A) alkanes
B) alkenes
C) alkynes
D) cyclic alkanes
24. The half-life of cobalt-60 is 5.3 yr. How much of a 1.000-mg sample of cobalt-60 is left after a 10.6yr
priod?
A) 0.250mg
B) 0.100mg
C) 0.990mg
D) 0.125mg
25. Which of the following salts has a cation that can hydrolyze in water?
A) NaCl
B) Ca(NO3)2
C) Ba(C2H3O2)2
D) NH4Cl
26. The unit of the rate constant for a second order reaction could be _______.
A) M-1 s-1
B) M
C) M s-1
D) M2s-1
27. For the reaction: A(g) + 2B(g)  4C(g), G = 77.8 kJ. If the reaction mixture consists of 2.0 atm A,
4.0 atm B, and 2.5 atm C at 298 K, calculate the G for this reaction mixture at 298 K. (R=8.314 J/molK).
A) 78.3 kJ
B) 7.89 kJ
C) –7.89 kJ
D) -34.2 kJ
28. A galvanic cell is composed of these two half cells, with the standard reduction
15
potentials shown
Zn2+(aq) + 2e- ↔ Zn(s)
-0.76 volt
Cd2+(aq) + 2e- ↔ Cd(s)
-0.40 volt
What is the standard free energy for the cell reaction of this galvanic cell?
A) -69 KJ
B) +69 KJ
C) -224 KJ
D) +224 KJ
29. The reaction 2H2O2  2H2O + O2 has the following mechanism?
H2O2 + I–  H2O + IO–
H2O + IO–  H2 + O2 + I–
The intermediates in the reaction are:
A) H2O and IO–
B) H2O2 and I–
C) H2O2 and IO–
D) IO– and I–
30. Name the following compound according to IUPAC system:
CH3

CH3CHCHCH2CH3

CH2CH3
A) 2,3-dimethylhexane
C) 3-ethyl-2-methylheptane
B) 3-ethyl-2,4-dimethylheptane
D) None of the above
31. The system, H2 (g) + X2 (g) ↔ 2 HX(g) has a value of 24.4 for the constant, Kc. A system being tried
in a 3.00 liter reactor was charged with 0.150 moles of H2, 0.150 moles of X2 and, 0.600 moles of HX. The
catalyst was introduced using a remote unit, and the system was allowed to come to equilibrium. Which
statement below describes the situation?
A) the reaction goes to the right, Q ‹ K
B) the reaction goes to the left, Q ‹ K
C) the reaction goes to the right, Q › K
D) the reaction goes to the left, Q › K
32. A solution is made by mixing 138.2 grams of ethanol, C2H6O, (46.069 g mol-1), 103.6 gram of water
(18.015 g mol-1), and 80.11 grams of methanol, CH4O, (32.0042 g mol-1). What is the mole fraction of
methanol in the mixture?
A) 0.02504
B) 0.2224
C) 0.2493
D) 0.3333
33. A Lewis base is defined as a substance that
A) acts as a proton donor
C) decreases [OH–] when placed in H2O
B) increases [H+] when placed in H2O
D) acts as a electron pair donor
34. The standard reduction potentials for the following half reactions are given as follows;
Cr+3 +3e-  Cr(s)
Br2(aq) + 2e-  2Br-
E0 = - 0.73 V
E0 = + 1.09 V
What is the E0 for this cell?
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A) 1.82 V
B) 0.36
C) 4.75 V
D) 1.79 V
35. Classify the following molecule:
O
CH3 - CH2 - CH2 - C O -CH3
A) ester
B) aldehyde
C) ketone
D) carboxylic acid
Name :__________________________
Part II-( 5 points each)
Show work- Please write your complete work in space provided.
Partial credit will be given.
1. Solution made by dissolving 6.73 grams of toluic acid in 110 grams of benzene ( f.p. = 5.45oC, Kf = 5.07
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o
C/m) gave a freezing point of 3.00 oC. What is the calculated molecular weight of toluic acid form this
data?
2. The gas phase decomposition of HI, HI(g) → 1/2H2(g) + 1/2I2(g) , has the rate equation,
-∆ [HI] / ∆t = K[HI]2 where K=30.0 L/mol. min at 443°C. How much time does it take for the
concentration of HI to drop from 0.010 mol/L to 0.0050 mol/L at 443°C?
3. Ka for hypochlorous acid, HClO, is 3.0x10-8.
a. Calculate the pH after addition of 15.0 ml of 0.100 M NaOH to 40.0 ml of 0.100 M HClO.
b. Identify the pH at half equivalent point.
4. Assuming that the value of ∆H and ∆S do not change with temperature, and using the following data,
CaO(s), ∆Hfo = -635.5 KJ mol-1, So = +40.0 J mol-1 K-1
CaCO3(s), ∆Hfo = -1207 KJ mol-1, So = +92.9 J mol-1 K-1
CO2(g), ∆Hfo = -394 KJ mol-1, So = +213.6 J mol-1 K-1
Calculate the value for the free energy change, ∆Go for the reaction,
CaCO3(s) → CaO(s) + CO2(g) at 815 Co
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5. Aluminum metal is oxidized in aqueous base with water serving as the oxidizing agent.
Al(s) + H2O(1) → Al(OH)4- + H2(g) (basic solution)
Write a balanced equation for this reaction in basic solution.
6. Refer to the following half-reactions below;
MnO4- + 8H+ + 5e-  Mn2+ + 4H2O
Cr2O72- + 14H+ + 6e-  2Cr3+ + 7H2O
E0 = 1.51 V
E0 = 1.33 V
Calculate the value of equilibrium constant at 25 0C for this reaction?
CHEMISTRY FINAL CHEM 1412B EXAM(answers)
PART - I
1. C 2. B 3. D 4. C 5. B 6. D 7. C 8. D 9. C 10. B 11. A 12. B 13. D 14. D 15. C
16. D 17. C 18. A 19. B 20. B 21. D 22. D 23. C 24. A 25. D 26. A 27. A 28. A 29. A 30. D
31. A 32. B 33. D 34. A 35. A
PART - II
1. ∆Tf = kf x m = kf x (n/kg) = (kf x m)/(Mxkg); M = (kf x m)/(∆Tf x kg)
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M = 136.15 g/mol
2. t = (1/k) x ((1/[A]t ) – (1/[A]o))
t = (1/30) x ((1/0.005) – (1/0.01))
t = 3.33 min.
3. a. pH = pKa + log((1.5x10-3)/(2.5x10-3))
pH = 7.30
b. At ½ equivalent point pH = pKa
pH = 7.52
4. ∆Ho = 177.5 kJ
∆So = 160.7 J
∆Go = ∆Ho - T∆So
∆Go = 177.5 kJ - 1088.15 x 160.7 x 10-3 kJ
∆Go = 2.634 kJ
5. 2Al + 6H2O + 2OH-  2Al(OH) 4 - + 3H2
6. ∆G = ∆Go + RT Ln Q
E = Eo – (RT/nF)Ln Q
E = Eo – (0.0592/n)Log Q
at equilibrium, E= 0, and Q = Keq.
Log Keq. = n Eo /0.0592 = 30 x (151 – 1.33)/0.0592
Log Keq. = 91.2;
Keq. = 1.58x1091
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