Republic of the Philippines
CARLOS HILADO MEMORIAL STATE COLLEGE
Talisay Main Campus
COLLEGE OF INDUSTRIAL TECHNOLOGY
B.S. CIVIL ENGINEERING
MIDTERM EXAMINATION IN CHEMISTRY FOR ENGINEERS (ENCHEM 114)
Name: _____________________________________________
Year/Section: _______________________________________
Date: _____________________
Score: ____________________
I. Multiple Choice: Write the letter of the best answer on your answer sheet. Use CAPITAL LETTER. One point
each.
1. The substance that changes the speed of the reaction is:
A. an oxidizing agent B. a reducing agent C. a bleaching agent
D. a catalyst.
2. The chemical symbol of aluminum sulfate is
A. AlSO4
B. Al2SO4
C. Al2(SO4)3
D. Al(SO4)3
3. Which of the following temperature scales will not give a negative temperature?
A. Kelvin
B. Celsius
C. Fahrenheit
D. All of the above
4. A substance which in molten state or in solution form allows electric current to pass through it is called
A. electrolyte
B. insulator
C. conduction
D. none of these
5. In an electrical connection between cathode and anode of voltaic cell, electrons flow from the
A. anode to the cathode
B. cathode to the anode C. either A. or B.
D. neither A. nor B.
6. Oxidation number of oxygen in OF2 is
A. + 1
B. – 1
C. + 2
D. – 2
7. In a galvanic cell, the reaction occurs 2H2O → O2 (g) + 4H+ + 4e . It occurs at the
A. cathode
B. anode
C. cathode and anode D. none of the above
8. Which of the following compounds is nonelectrolyte?
A. sodium chloride (NaCl)
C. ammonium hydroxide (NH4OH)
B. sulfuric acid (H2SO4)
D. carbon tetrachloride (CCI4)
–
9. Which statement below is not true for the reaction Fe3+ + e – → Fe2+
A. Fe3+ is reduced
C. oxidation state of Fe has changed
B. Fe3+ can act as an oxidizing agent
D. both Fe2+ and Fe3+ are called anions.
10. In the reaction 2Fe + Cl2 → 2FeCl3
A. Fe is reduced B. Fe is oxidized
C. Cl2 is oxidized
D. none of these.
11. During a redox reaction, an oxidizing agent
A. gains electrons
B. is oxidized
C. loses electrons D. is hydrolyzed.
12. When aqueous solution of NaCl is electrolyzed
A. Cl2 is evolved at the cathode
C. H2 is evolved at cathode
B. Na is deposited at the cathode
D. Na appears at the anode
13. An electrochemical cell consists of two copper electrodes dipping into aqueous CuSO4 solution; the electrodes
are connected to a battery. Which statement about the electrolysis process in this cell is incorrect?
A. Copper are deposited on the cathode.
C. Cu2+ ions are produced at the anode.
B. Copper is transferred from anode to cathode.
D. Reduction occurs at the anode.
14. A physical or chemical process that occurs by itself is called
A. non spontaneous
B. self-occurring
C. spontaneous
D. thermodynamic
15. In the reaction of Sn2+ with ClO3- to form Cl- and Sn4+ in acid solution, what is the change in the oxidation number
of Cl?
A. a decrease of 6
B. a decrease of 4
C. a decrease of 2
D. an increase of 2.
16. The amount of energy necessary to remove an electron in the last energy level of an atom is called:
A. ionization energy
B. electron affinity
C. potential energy
D. chemical energy.
17. A lead storage cell can function both as an electrolytic cell and as a voltaic cell. When a lead storage battery is
being recharged, it converts _______ energy to _______ energy.
A. chemical; electrical
B. electrical; chemical
C. chemical; heat
D. electrical; mechanical
18. Which of the following statements is incorrect?
A. An external power supply is needed in an electrolytic cell.
B. In a galvanic cell, the passage of a current through an electrolyte drives a redox reaction.
C. In a Daniell cell, a difference in electrical potentials of the two half-cells results in a flow of electrons between
the half-cells.
D. Copper can be purified using an electrolytic cell.
19. The e.m.f. produced by a voltage cell is
A. electrode potential
B. reduction potential
C. cell potential
D. oxidation potential
20. When the current is passed through an electrolytic solution, which of the following process will occur
A. cations and anions both move towards anode
C. cations and anions both move towards anode
B. no movement of the ions occur
D. anions move towards anode and cations move towards cathode
21. When a radioactive nucleus emits an alpha particle, the mass of the atom:
A. Remains same and its atomic number decreases.
C. Decreases and its atomic number increases.
B. Decreases and its atomic number decreases.
D. Increases and its atomic number decreases.
0
4+
3+
2+
22. Values of E for the Ce /Ce and Fe /Fe half-cells are +1.72 and - 0.44V, respectively. From these data you can
conclude that:
A. Ce3+ is a better oxidizing agent than Fe2+
C. Ce3+ will oxidize Fe.
4+
2+
B. Ce is a better oxidizing agent than Fe
D. Ce4+ will oxidize Fe2+.
23. Which of these chemical reactions is an oxidation-reduction reaction?
A Fe  S  FeS
C. AgNO3  NaCl  AgCl  NaNO3
B. CO2  H 2O  H 2CO3
D. H 2 SO4  2 NaOH  Na 2 SO4  2 H 2O
24. The nucleus of radioactive element possesses
A. zero binding energy
B. high potential energy
C. high binding energy
D. low binding energy.
2
3
25. Given the equation: 2Cr s   3Pb aq   2Cr aq   3Pbs  , which is the correct reduction half
reaction?
A. Cr s   Cr 3 aq   3e 
C. Pb 2 aq   Pbs   2e 
B. Cr s   3e   Cr 3 aq 
D. Pb 2 aq   2e   Pbs 
26. Large energy released in an atomic bomb explosion is mainly due to
A. Products having a lesser mass than initial substance C. release of electrons
B. release of protons
D. conversion of heavier to lighter atoms.
27. The source of solar energy is A. natural radioactivity B. nuclear fusion C. nuclear fission D. combustion of H2.
28. In these incomplete half-reactions which reactant is an oxidizing agent?
Ag s   Ag  aq  ;
Cl  aq   Cl 2  g  ;
Fe3 aq   Fe 2 aq  ;
Sn 2 aq   Sn 4 aq 
A. Ag(s)
B. Cl- (aq)
C. Fe3+ (aq)
D. Sn2+ (aq)
29. A stable nuclide has, in general,
A. even number of protons and even number of neutrons C. odd number of protons and odd number of neutrons
B. odd number of protons and even number of electrons D. equal numbers of protons and neutrons.
30. In which equation is the metal reduced?

2

2
A. 2 MnO4  5C2O4  16 H  2Mn  10CO2  8H 2O
B. CuCO3  2 HCl  CuCl 2  CO2  H 2O
C.
Cr2O72  2OH   2CrO42  H 2O
D.
Mg  2 HCl  MgCl 2  H 2
II. PROBLEM SOLVING: Multiple Choice: Show your solution on a yellow paper and write the letter of the best answer.
Use CAPITAL LETTERS only. Three points each. No points for answers without a correct solution.
31. The half-life of a radioactive element is 50 days. How long will it take for the activity to reduce to ¼
of its original value?
A. 100 days
B. 75 days
C. 50 days
D. 25 days
32. A certain nuclide has a half-life period of 30 minutes. If a sample containing 600 atoms is allowed to
decay for 90 minutes, how many atoms will disappear?
A. 425 atoms
B. 350 atoms C. 150 atoms
D. 525 atoms
33. Consider the following unbalanced redox equation
 CH 3OH l   Cr2O7 aq    H  aq   CH 2O aq   Cr 3 aq   H 2O l  . Which of the following sets
of numbers will balance the equation?
A. 1,1,14,1,2,7
B. 3,1,8,3,2,7
C. 3,1,8,3,2,8
D. 3,1,14,3,2,8
34. 48,000 coulomb of charge is required to deposit one-sixth of a mole of a metal. The metal is most likely
to be ….
A. Ca
B. Al
C. Na
D. Mg
35. When a mass equal to 1 amu disappears, the energy produced is equal to nearly
A. 932 J
B. 329 eV
C. 932 eV
D. 932 MeV
36. The masses of neutron and proton are 1.0087 and 1.0073 amu respectively. If the neutrons proton
combine to form helium nucleus of mass 4.0015 amu, the binding energy of helium nucleus would be
A. 28.4 MeV
B. 20.8 MeV
C. 27.3 MeV
D. 14.2 MeV
37. How much Cu metal is produced at the cathode during the electrolysis of aqueous CuSO4 solution if a
current of 0.10 A passes through the solutions for 20 min?
A. 2.0 x 10-5 moles
B. 1.2 x 10-3 moles
C. 1.0 x 10-5 moles
D. 6.2 x 10-4 moles
38. For the reaction: 2 H   Mg  H 2  Mg 2
ΔG0 = - 457 kJ/mole. What is the value of E0 (Mg2+ /Mg)?
A. -2.37 V
B. -4.74 V
C. 2.37 V
D. 4.74 V
39. What is the value of ΔG0 (298K) for the reaction between Cl2 and I- ions if the E0 values for the Cl2/Cl- and
I2 /I- half-cells are 1.36 and 0.754 V, respectively? Give your answer per mole of Cl2.
A. -59 kJ/mole
B. -118 J/mole
C. 59 J/mole
D. 118 kJ/mole
40. E0 (Cu2+ /Cu) = 0.34 V. What is the value of E (at 298K) for an aqueous solution in which [Cu2+] = 0.02 mol dm-3
A. 0.36 V
B. 0.29 V
C. 0.32 V
D. 0.39
2
III. Problems: Show your detailed solution on a yellow paper. Ten points each
41. Balance the following equation in basic solution:
MnO₄⁻ + CN⁻ → MnO₂ + CNO⁻
42. Find the emf of the cell: Pbs , PbSO4 / SO4
2
0.1M  // Pb 2 0 / 004M  / Pbs 
E 0 PbSO 4 / Pb , SO42   0.359V and E 0 Pb 2 / Pb  0.126V
43. If the decrease between 18. and 24. years in mass of radioactive matter is 4g, find its initial mass. Half life
of this matter is 6 years.
44. An electroplating bath is used to plate a uniform layer of silver metal of thickness 0.1 mm onto an object
of total surface area 300 cm2. Given that the density of silver is 10.5 g cm-3. How long will a current of 2 A
be passed through the cell to plate the object?
=========================================E N D========================================
Prepared by:
Engr. MARLYN G. JOVER, PhDTM
Instructor
Reviewed by:
Engr. GRACE C. GERONA
Chairperson, BSCE
Key Answer (Introduction to Electrochemistry)
Republic of the Philippines
CARLOS HILADO MEMORIAL STATE COLLEGE
Talisay Main Campus
COLLEGE OF INDUSTRIAL TECHNOLOGY
B.S. CIVIL ENGINEERING
MIDTERM EXAMINATION IN CHEMISTRY FOR ENGINEERS (ENCHEM 114)
Name: _____________________________________________
Year/Section: _______________________________________
Date: _____________________
Score: ____________________
II. Multiple Choice: Write the letter of the best answer on your answer sheet. Use CAPITAL LETTER. One point
each.
1. The substance that changes the speed of the reaction is:
B. an oxidizing agent B. a reducing agent C. a bleaching agent
D. a catalyst.
2. The chemical symbol of aluminum sulfate is
A. AlSO4
B. Al2SO4
C. Al2(SO4)3
D. Al(SO4)3
3. Which of the following temperature scales will not give a negative temperature?
A. Kelvin
B. Celsius
C. Fahrenheit
D. All of the above
4. A substance which in molten state or in solution form allows electric current to pass through it is called
A. electrolyte
B. insulator
C. conduction
D. none of these
5. In an electrical connection between cathode and anode of voltaic cell, electrons flow from the
A. anode to the cathode
B. cathode to the anode C. either A. or B.
D. neither A. nor B.
6. Oxidation number of oxygen in OF2 is
A. + 1
B. – 1
C. + 2
D. – 2
7. In a galvanic cell, the reaction occurs 2H2O → O2 (g) + 4H+ + 4e–. It occurs at the
A. cathode
B. anode
C. cathode and anode D. none of the above
8. Which of the following compounds is nonelectrolyte?
A. sodium chloride (NaCl)
C. ammonium hydroxide (NH4OH)
B. sulfuric acid (H2SO4)
D. carbon tetrachloride (CCI4)
9. Which statement below is not true for the reaction Fe3+ + e – → Fe2+
A. Fe3+ is reduced
C. oxidation state of Fe has changed
3+
B. Fe can act as an oxidizing agent
D. both Fe2+ and Fe3+ are called anions.
10. In the reaction 2Fe + Cl2 → 2FeCl3
A. Fe is reduced B. Fe is oxidized
C. Cl2 is oxidized
D. none of these.
11. During a redox reaction, an oxidizing agent
A. gains electrons
B. is oxidized
C. loses electrons D. is hydrolyzed.
12. When aqueous solution of NaCl is electrolyzed
A. Cl2 is evolved at the cathode
C. H2 is evolved at cathode
B. Na is deposited at the cathode
D. Na appears at the anode
13. An electrochemical cell consists of two copper electrodes dipping into aqueous CuSO4 solution; the electrodes
are connected to a battery. Which statement about the electrolysis process in this cell is incorrect?
A. Copper are deposited on the cathode.
C. Cu2+ ions are produced at the anode.
B. Copper is transferred from anode to cathode.
D. Reduction occurs at the anode.
Same as Number 8.
14. A physical or chemical process that occurs by itself is called
A. non spontaneous
B. self-occurring
C. spontaneous
D. thermodynamic
15. In the reaction of Sn2+ with ClO3- to form Cl- and Sn4+ in acid solution, what is the change in the oxidation number
of Cl?
A. a decrease of 6
B. a decrease of 4
C. a decrease of 2
D. an increase of 2.
16. The amount of energy necessary to remove an electron in the last energy level of an atom is called:
A. ionization energy
B. electron affinity
C. potential energy
D. chemical energy.
17. A lead storage cell can function both as an electrolytic cell and as a voltaic cell. When a lead storage battery is
being recharged, it converts _______ energy to _______ energy.
A. chemical; electrical
B. electrical; chemical
C. chemical; heat
D. electrical; mechanical
18. Which of the following statements is incorrect?
A. An external power supply is needed in an electrolytic cell.
B. In a galvanic cell, the passage of a current through an electrolyte drives a redox reaction.
C. In a Daniell cell, a difference in electrical potentials of the two half-cells results in a flow of electrons between
the half-cells.
D. Copper can be purified using an electrolytic cell.
19. The e.m.f. produced by a voltage cell is
A. electrode potential
B. reduction potential
C. cell potential
D. oxidation potential
20. When the current is passed through an electrolytic solution, which of the following process will occur
A. cations and anions both move towards anode
C. cations and anions both move towards anode
B. no movement of the ions occur
D. anions move towards anode and cations move towards cathode
21. When a radioactive nucleus emits an alpha particle, the mass of the atom:
A. Remains same and its atomic number decreases.
C. Decreases and its atomic number increases.
B. Decreases and its atomic number decreases.
D. Increases and its atomic number decreases.
22. Values of E0 for the Ce4+ /Ce3+ and Fe2+ /Fe half-cells are +1.72 and - 0.44V, respectively. From these data you can
conclude that:
A. Ce3+ is a better oxidizing agent than Fe2+
C. Ce3+ will oxidize Fe.
4+
2+
B. Ce is a better oxidizing agent than Fe
D. Ce4+ will oxidize Fe2+.
23. Which of these chemical reactions is an oxidation-reduction reaction?
A Fe  S  FeS
C. AgNO3  NaCl  AgCl  NaNO3
B. CO2  H 2O  H 2CO3
D. H 2 SO4  2 NaOH  Na 2 SO4  2 H 2O
24. The nucleus of radioactive element possesses
A. zero binding energy
B. high potential energy
C. high binding energy
D. low binding energy.
2
3
25. Given the equation: 2Cr s   3Pb aq   2Cr aq   3Pbs  , which is the correct reduction half
reaction?
A. Cr s   Cr 3 aq   3e 
C. Pb 2 aq   Pbs   2e 
B. Cr s   3e   Cr 3 aq 
D. Pb 2 aq   2e   Pbs 
26. Large energy released in an atomic bomb explosion is mainly due to
A. Products having a lesser mass than initial substance C. release of electrons
B. release of protons
D. conversion of heavier to lighter atoms.
27. The source of solar energy is A. natural radioactivity B. nuclear fusion C. nuclear fission D. combustion of H2.
28. In these incomplete half-reactions which reactant is an oxidizing agent?
Ag s   Ag  aq  ;
Cl  aq   Cl 2  g  ;
Fe3 aq   Fe 2 aq  ;
Sn 2 aq   Sn 4 aq 
A. Ag(s)
B. Cl- (aq)
C. Fe3+ (aq)
D. Sn2+ (aq)
29. A stable nuclide has, in general,
A. even number of protons and even number of neutrons C. odd number of protons and odd number of neutrons
B. odd number of protons and even number of electrons D. equal numbers of protons and neutrons.
30. In which equation is the metal reduced?
A.
2 MnO4  5C2O42  16 H   2Mn 2  10CO2  8H 2O
B.
C.
D.
CuCO3  2 HCl  CuCl2  CO2  H 2O
Cr2O72  2OH   2CrO42  H 2O
Mg  2 HCl  MgCl 2  H 2
III. PROBLEM SOLVING: (3pts each) Multiple Choice: Show your solution on a yellow paper and write the letter of the
best answer. Use CAPITAL LETTERS only. Three points each. No points for answers without a correct solution.
31. The half-life of a radioactive element is 50 days. How long will it take for the activity to reduce to ¼
of its original value?
A. 100 days
B. 75 days
C. 50 days
D. 25 days
Solution: ln(1/4) = - (ln2/50)t;
t = 100 days
32. A certain nuclide has a half-life period of 30 minutes. If a sample containing 600 atoms is allowed to
decay for 90 minutes, how many atoms will disappear?
A. 425 atoms
B. 350 atoms C. 150 atoms
D. 525 atoms
-2.07949
Solution: ln(NF/600) = - (ln2/30)90; NF = (e
)600 = 525
33. Consider the following unbalanced redox equation
 CH 3OH l   Cr2O7 aq    H  aq   CH 2O aq   Cr 3 aq   H 2O l  . Which of the following sets
of numbers will balance the equation?
A. 1,1,14,1,2,7
B. 3,1,8,3,2,7
C. 3,1,8,3,2,8
D. 3,1,14,3,2,8
Solution:
2
34. 48,000 coulombs of charge is required to deposit one-sixth of a mole of a metal. The metal is most likely
to be ….
A. Ca
B. Al
C. Na
Solution: 96,500 coul/mole = 48,000 cuol/(1/6)mole = 2.98 = 3
D. Mg
35. When a mass equal to 1 amu disappears, the energy produced is equal to nearly
A. 932 J
B. 329 eV
C. 932 eV
D. 932 MeV
2
-27
8 2
Solution: E = mc = 1 amu(1.66052x10 kg /amu)(3x10 ) / (1 MeV/1.66x1019 J) = 932 MeV
36. The masses of neutron and proton are 1.0087 and 1.0073 amu respectively. If the neutrons proton
combine to form helium nucleus of mass 4.0015 amu, the binding energy of helium nucleus would be
A. 28.4 MeV
B. 20.8 MeV
C. 27.3 MeV
D. 14.2 MeV
2
-29
8 2
-12
Solution: BE = ∆mc = 5.065x10 (3x10 ) = 4.56 x 10 J(1 eV/1.602x10-19 J) = 28.4 MeV
m  21.0073   21.0087   4.0015  0.0305 amu
 1.6605x10 27 kg 
  5.06510  29 kg
 0.0305amu 
1
amu


37. How much Cu metal is produced at the cathode during the electrolysis of aqueous CuSO4 solution if a
current of 0.10 A passes through the solutions for 20 min?
A. 2.0 x 10-5 moles
B. 1.2 x 10-3 moles
C. 1.0 x 10-5 moles
D. 6.2 x 10 -4 moles
1mole 
1molCu
Solution: m =Kit = 0.10 A(20 x60s )(
)(
)  6.2.1x10  4 mol

96500Coul 2mole
38. For the reaction: 2 H   Mg  H 2  Mg 2
A. - 2.37 V
B. - 4.74 V
Solution: G = -nFE
cell
ΔG0 = - 457 kJ/mole. What is the value of E0 (Mg2+ /Mg)?
C. 2.37 V
D. 4.74 V
-457,00 = - 2(96,500) E
cell
E
ce
= 2.37 V
39. What is the value of ΔG0 (298K) for the reaction between Cl2 and I- ions if the E0 values for the Cl2/Cl- and
I2 /I- half-cells are 1.36 and 0.754 V, respectively? Give your answer per mole of Cl2.
A. -59 kJ/mole
B. -118 J/mole
C. 59 J/mole
D. 118 kJ/mole
Solution: G = -nFE
cell
= - 1(96,500)(0.606)
= - 59 kJ/mole
40. E0 (Cu2+ /Cu) = 0.34 V. What is the value of E (at 298K) for an aqueous solution in which [Cu2+] = 0.02 mol dm-3
A. 0.36 V
B. 0.29 V
C. 0.32 V
D. 0.39
0.0592 V
Solution: E  E o 
log Q
n
0.0592 V
E  0.34V 
log 0.2
2
E = 0.39 V
III. Problems: (10 pts each) Show your detailed solution on a yellow paper. Ten points each
41. Balance the following equation in basic solution:
MnO₄⁻ + CN⁻ → MnO₂ + CNO⁻
Solution:
+7
+4
MnO₄⁻ → MnO₂ ;
+7
+4
_1
+1
CN⁻ → CNO⁻
_1
+1
(MnO₄⁻ + 3e → MnO₂ )2 ;
(CN⁻ → + 2e + CNO⁻)3
2MnO₄⁻ + 6e → 2MnO₂ ;
3CN⁻ → + 6e + 3CNO⁻
2MnO₄⁻ + 3CN⁻ + 2H + 2OH- → 2MnO₂ + 3CNO⁻ + H2O + 2OH2MnO₄⁻ + 3CN⁻ + 2H2O - → 2MnO₂ + 3CNO⁻ + H2O + 2OH2MnO₄⁻ + 3CN⁻ + H2O - → 2MnO₂ + 3CNO⁻ + 2OH42. Find the emf of the cell : Pbs , PbSO4 / SO4
2
0.1M  // Pb 2 0 / 004M  / Pbs 
E 0 PbSO 4 / Pb , SO42   0.359V and E 0 Pb 2 / Pb  0.126V
0.0592 V
product
log
n
reac tan t
0.0592
0.004
E  0.485 
log
2
0 .1
E  0.485  ( 0.04138 )  0.44362 V
Solution: E  E o 
43. If the decrease between 18. and 24. years in mass of radioactive matter is 4g, find its initial mass. Half life
of this matter is 6 years.
Solution:
ln
Nt
  kt
N0
;
ln
Nt
ln 2
  1/ 2 t
N0
t
Nt
0.693

24
N0
6
4g
0.693
ln

24
N0
6
ln
No = 64 g
44. An electroplating bath is used to plate a uniform layer of silver metal of thickness 0.1 mm onto an object
of total surface area 300 cm2. Given that the density of silver is 10.5 g cm-3. How long will a current of 2 A
be passed through the cell to plate the object?
ρ = m/V; V = hxA = 0.1 x10-2 cm(300 cm2) = 3x10-1 m3
m = ρV = 10.5 g cm-3(3x10-1 m3 ) = 3.15 g
m = Kit;


 96,500 As  1  1mole

 = 1447.5 s = 0.40 hr
t = 3.15 x10 3 kg 


3

 1mole  2 A  108 x10 kg 
=========================================E N D========================================
Prepared by:
Engr. MARLYN G. JOVER, PhDTM
Instructor
Reviewed by:
Engr. GRACE C. GERONA
Chairperson, BSCE