CHEM 2 EXAM 3

Which one of the following can be done to shorten the half-life of the radioactive decay of uranium-238? A) heat it B) oxidize it to the +2 oxidation state C) freeze it D) convert it to UF6 E) none of the above

E

Which transformation could take place at the anode of an electrochemical cell A) F2 to F- B) Cr2O7²- → Cr2+ C) O2 to H2O D) HAsO2 to As E) None of the above could take place at the anode.

E

The half-life of a radionuclide A) is constant. B) gets longer with increased temperature. C) gets longer with passing time. D) gets shorter with increased temperature. E) gets shorter with passing time.

A

Alcohols are hydrocarbon derivatives in which one or more hydrogens have been replaced by a hydroxyl functional group. __________ is the general formula of an alcohol A) R-OH B) R-CO-H C) R-O-R D) R-CO-OH E) R-CO-R

A

By what process does thorium-230 decay to radium-226? A) alpha emission B) beta emission C) positron emission D) electron capture E) gamma emission

A

Cathodic protection of a metal pipe against corrosion usually entails A) attaching an active metal to make the pipe the anode in an electrochemical cell. B) coating the pipe with another metal whose standard reduction potential is less negative than that of the pipe. C) attaching a dry cell to reduce any metal ions which might be formed. D) coating the pipe with a fluoropolymer to act as a source of fluoride ion (since the latter is so hard to oxidize). E) attaching an active metal to make the pipe the cathode in an electrochemical cell.

A

Corrosion of iron is retarded by __________ A) high pH conditions B) the presence of salts C) low pH conditions D) both the presence of salts and high pH conditions E) both the presence of salts and low pH conditions

A

Galvanized iron is iron coated with __________. A) zinc. B) chromium. C) phosphate. D) magnesium. E) iron oxide.

A

How many grams of CuS are obtained by passing a current of 12 A through a solution of CuSO4 for 15 minutes __________ A) 3.6 B) 1.8 C) 14 D) 7.1 E) .016

A

How many minutes will it take to plate out 2.19 g of chromium metal from a solution of Cr3+ using a current of 35.2 amps in an electrolyte cell __________ A) 5.77 B) 17.3 C) 1.92 D) 346 E) 115

A

The balanced half-reaction in which chlorine gas is reduced to the aqueous chloride ion is a 11) __________ process. A) two-electron B) six-electron C) four-electron D) one-electron E) three-electron

A

The gain of electrons by an element is called __________. A) reduction B) oxidation C) fractionation D) sublimation E) disproportionation

A

The standard cell potential (E°cell) for the reaction below is +1.10 V. The cell potential for this 28) reaction is __________ V when the concentration of [Cu2+] = 1.0 × 10-5 M and [Zn2+] = 1.0 M. Zn (s) + Cu2+ (aq) → Cu (s) + Zn2+ (aq) A) 0.95 B) 1.25 C) 1.10 D) 0.80 E) 1.40

A

The standard cell potential (E°cell) of the reaction below is +0.126 V. The value of ΔG° for the 26) reaction is __________ kJ/mol Pb (s) + 2H+ (aq) → Pb2+ (aq) + H2 (g) A) -24 B) +24 C) -12 D) +12 E) -50

A

The standard cell potential (E°cell) of the reaction below is +0.126 V. The value of ΔG° for the reaction is__________ kJ/mol. Pb(s) + 2H+(aq) → Pb2+(aq) +H2(g) A) -24 B) +24 C) -12 D) +12 E) -50

A

The town of Natrium, West Virginia, derives its name from the sodium produced in the electrolysis of molten sodium chloride (NaCl) mined from ancient salt deposits. The number of kilowatt-hours of electricity required to produce 4.60 kg of metallic sodium from the electrolysis of molten NaCl(s) is __________ when the applied emf is 4.50 V. A) 0.0241 B) 24.1 C) 12.1 D) 0.0414 E) 48.3

A

What drives the turbine in a nuclear power plant? A) steam B) the control rods C) the primary coolant D) the moderator E) UF6 gas

A

Which one of the following is the best oxidizing agent ? A) Na B) H2 C) O2 D) Ca E) Li

A

Which substance is serving as the reducing agent in the following reaction? 14H+ + Cr2O7²- + 3Ni → 3Ni²+ + 2Cr³+ + 7H2O A) Ni B) H2O C) Cr2O7 D) Ni E) H+

A

Which transformation could take place at the cathode of an electrochemical cell A) Br2 → BrO3- B) NO → HNO2 C) HSO4- → H2SO3 D) MnO2 → MnO4- E) Mn2+ → MnO4-

A

__________ electrons appear in the following half-reaction when it is balanced S4O6²- → 2S2O3²- A) 2 B) 4 C) 3 D) 1 E) 6

A

__________ electrons appear in the following half-reaction when it is balanced. S4O6²- → 2S2O3²- A) 2 B) 4 C) 6 D) 3 E) 1

A

What is required for a nuclear transmutation to occur? A) very high temperature B) gamma emission C) spontaneous nuclear decay D) a corrosive environment E) a particle to collide with a nucleus

E

1V = __________. A) 1 amp · s B) 1 J/C C) 96485 C D) 1 J/s E) 1 C/J

B

One of the differences between a voltaic cell and an electrolytic cell is that in an electrolytic cell __________ A) electrons flow toward the anode B) a nonspontaneous reaction is forced to occur C) an electric current is produced by a chemical reaction D) O2 gas is produced at the cathode E) oxidation occurs at the cathode

B

The balanced half-reaction in which dichromate ion is reduced to chromium(III) ion is a __________ process. A) three-electron B) six-electron C) twelve-electron D) four-electron E) two-electron

B

The electrolysis of molten AlCl3 for 3.25 hr with an electrical current of 15.0 A produces __________ g of aluminum metal. A) 16.4 B) 147 C) 49.1 D) 0.606 E) 4.55 × 10-3

B

The standard emf for the cell using the overall cell reaction below is +2.20 V: 2Al (s) + 3I2 (s) → 2Al3+ (aq) + 6I- (aq) The emf generated by the cell when [Al3+] = 4.5 × 10-3 M and [I-] = 0.15 M is ________ V. A) 2.39 B) 2.20 C) 2.23 D) 2.30 E) 2.10

B

What happens to the mass number and the atomic number of an element when it undergoes beta decay? A) The mass number decreases by 4 and the atomic number decreases by 2. B) The mass number does not change and the atomic number increases by 1. C) The mass number increases by 2 and the atomic number increases by 1. D) The mass number does not change and the atomic number decreases by 2. E) Neither the mass number nor the atomic number change.

B

What is emitted in the nuclear transmutation, ²⁷₁₃ Al(n, ?) ²⁴₁₁Na? A) a proton B) an alpha particle C) a gamma photon D) a beta particle E) a neutron

B

Which type of radioactive decay results in no change in mass number and atomic number for the starting nucleus? A) beta B) gamma C) electron capture D) positron emission E) alpha

B

___ is reduced in the following reaction: Cr2O7²- + 6S2O3²- + 14H+ → 2Cr³+ + 3S4O6²- + 7H2O A) S4O6²- B) Cr2O7²- C) Cr³+ D) S2O3²- E) H+

B

Consider an electrochemical cell based on the reaction: 2H+(aq) + Sn(s) → Sn2+(aq) + H2(g) Which of the following actions would change the measured cell potential? A) increasing the [Sn2+] in the anode compartment B) increasing the pressure of hydrogen gas in the cathode compartment C) lowering the pH in the cathode compartment D) increasing the pH in the cathode compartment E) Any of the above will change the measure cell potential.

C

Half Reaction E˚ Cr 3+ (aq) + 3e ↔Cr (s) -.74 Fe 2+ (aq) + 2e ↔Fe (s) -.440 Fe 3+ (aq) + e ↔Fe2+ (s) +.771 Sn 4+ (aq) + 2e ↔Sn 2+ (s) +.154 The standard cell potential (Eecell) for the voltaic cell based on the reaction below is __________ V Cr (s) + 2Fe3+ (aq) ↔ 3Fe2+ (aq) + Cr3+ (aq) A) +1.57 B) +2.99 C) +1.51 D) +3.05 E) -1.45

C

Half Reaction E˚ Cr 3+ (aq) + 3e ↔Cr (s) -.74 Fe 2+ (aq) + 2e ↔Fe (s) -.440 Fe 3+ (aq) + e ↔Fe2+ (s) +.771 Sn 4+ (aq) + 2e ↔Sn 2+ (s) +.154 The standard cell potential (Eecell) for the voltaic cell based on the reaction below is __________ V Sn2+ (aq) + 2Fe3+ (aq) ↔ 2Fe2+ (aq) + Sn4+ (aq) A) -0.46 B) +0.46 C) +0.617 D) +1.39 E) +1.21

C

In the nuclear transmutation, ¹⁶₈ O (p, a) ¹³₇ N, what is the bombarding particle? A) a beta particle B) a phosphorus nucleus C) a proton D) a gamma photon E) an alpha particle

C

The balanced half-reaction in which dichromate ion is reduced to chromium metal is a __________ process. A) two-electron B) six-electron C) twelve-electron D) four-electron E) three-electron

C

The lead-containing reactant(s) consumed during recharging of a lead-acid battery is/are A) PbO2 (s) only B) Pb (s) only C) PbSO4 (s) only D) both PbO2 (s) and PbSO4 (s) E) both Pb (s) and PbO2 (s)

C

The purpose of the salt bridge in an electrochemical cell is to __________. A) provide a source of ions to react at the anode and cathode. B) provide a means for electrons to travel from the anode to the cathode. C) maintain electrical neutrality in the half-cells via migration of ions. D) provide a means for electrons to travel from the cathode to the anode. E) provide oxygen to facilitate oxidation at the anode.

C

The standard cell potential (E°) of a voltaic cell constructed using the cell reaction below is 0.76 V: Zn(s)+2H+(aq) → Zn2+(aq)+H2(g) With PH2 = 1.0 atm and [Zn2+] = 1.0 M, the cell potential is 0.66 V. The concentration of H+ in the cathode compartment is __________ M. A) 2.0 × 10-2 B) 1.0 × 10-12 C) 4.9 × 10 D) 4.2 × 10-4 E) 1.4 × 10-1

C

What is the oxidation number of chromium in Cr2O7 ²- ion? A) +12 B) +14 C) +6 D) +3 E) +7

C

What is the oxidation number of chromium in the dichromate ion? A) +12 B) +7 C) +6 D) +14 E) +3

C

What is the oxidation number of manganese in the MnO₄ ¹- ion? A) +4 B) +2 C) +7 D) +1 E) +3

C

What is the oxidation number of potassium in KMnO4? A) +3 B) 0 C) +1 D) -1 E) +2

C

Which of the following reactions is a redox reaction? (a) K2CrO4 + BaCl2 → BaCrO4 + 2KCl (b) Pb2²+ + 2Br- → PbBr (c) Cu + S → CuS A) a only B) b only C) c only D) b and c E) a and c

C

Which one of the following types of elements is most likely to be a good oxidizing agent? A) transition elements B) alkali metals C) halogens D) lanthanides E) alkaline earth elements

C

Which one of the following types of elements is most likely to be a good oxidizing agent? A) halogens B) alkaline earth elements C) lanthanides D) transition elements E) alkali metals

C

When ionizing radiation enters the body, what is the predominant free radical produced? A) H3O B) H C) protein D) H2O E) OH

E

Cathodic protection of a metal pipe against corrosion usually entails A) coating the pipe with another metal whose standard reduction potential is less negative than that of the pipe. B) coating the pipe with a fluoropolymer to act as a source of fluoride ion (since the latter is so hard to oxidize). C) attaching a dry cell to reduce any metal ions which might be formed. D) attaching an active metal to make the pipe the cathode in an electrochemical cell. E) attaching an active metal to make the pipe the anode in an electrochemical cell.

D

Consider an electrochemical cell based on the reaction: 2H+(aq) + Sn(s) → Sn2+(aq) + H2(g) Which of the following actions would not change the measured cell potential? A) lowering the pH in the cathode compartment B) increasing the pressure of hydrogen gas in the cathode compartment C) addition of more tin metal to the anode compartment D) increasing the tin (II) ion concentration in the anode compartment E) Any of the above will change the measured cell potential.

D

Galvanized iron is iron coated with __________ A) phosphate. B) magnesium. C) iron oxide. D) zinc. E) chromium.

D

Half Reaction E˚ Cr 3+ (aq) + 3e ↔Cr (s) -.74 Fe 2+ (aq) + 2e ↔Fe (s) -.440 Fe 3+ (aq) + e ↔Fe2+ (s) +.771 Sn 4+ (aq) + 2e ↔Sn 2+ (s) +.154 The standard cell potential (Eecell) for the voltaic cell based on the reaction below is __________ V 3Sn4+ (aq) + 2Cr (s) ↔ 2Cr3+ (aq) + Sn4+ (aq) A) -1.02 B) +2.53 C) -0.59 D) +0.89 E) +1.94

D

The electrode at which oxidation occurs is called the A) oxidizing agent B) reducing agent C) cathode D) anode E) voltaic cell

D

The more __________ the value of Eered, the greater the driving force for reduction. A) exothermic B) extensive C) negative D) positive

D

The relationship between the change in Gibbs free energy and the emf of an electrochemical cell is 25) given by __________. A) ΔG = -nF/ERT B) ΔG = -nF/E C)ΔG= -E/nF D) ΔG = -nFE E) ΔG = -nRTF

D

What is the missing product from this reaction? ³²₁₅P →³²₁₆S + _____ A) ⁴₂He B) ⁰₀ y C) ⁰₁ p D) ⁰₋₁e E) ⁰₁e

D

What is the oxidation number of manganese in MnO2? A) +2 B) +7 C) +1 D) +4 E) +3

D

Which substance is the reducing agent in the reaction below Pb + PbO2 + 2H2SO4 → 2PbSO4 + 2H2O A) PbSO4 B) PbO2 C) H2SO4 D) Pb E) H2O

D

A voltaic cell is constructed with two silver-silver chloride electrodes, where the half-reaction is AgCl(s)+e- → Ag(s)+Cl-(aq) E°=+0.222V The concentrations of chloride ion in the two compartments are 0.0222 M and 2.22 M, respectively. The cell emf is __________ V. A) 0.232 B) 0.118 C) 22.2 D) 0.212 E) 0.00222

E

Atoms with the same atomic number and different mass numbers A) are allotropes B) do not exist. C) are resonance structures. D) are isomers. E) are isotopes.

E

In a voltaic cell, electrons flow from the __________ to the __________. A) cathode, anode B) salt bridge, cathode C) anode, salt bridge D) salt bride, anode E) anode, cathode

E

In balancing the nuclear reaction ²⁹³₉₂U →²³⁴₉₀E + ⁴₂He, the identity of element E is A) Pu. B) Pa. C) U. D) Np. E) Th

E

Of the following processes, which one changes the atomic number? A) beta emission B) alpha emission C) electron capture D) positron emission E) All of these processes change the atomic numbers.

E

One of the differences between a voltaic cell and an electrolytic cell is that in an electrolytic cell __________ A) electrons flow toward the anode B) a nonspontaneous reaction is forced to occur C) O2 gas is produced at the cathode D) oxidation occurs at the cathode E) an electric current is produced by a chemical reaction

E

The balanced half-reaction in which sulfate ion is reduced to sulfite ion is a __________ process. A) three-electron B) six-electron C) four-electron D) one-electron E) two-electron

E

The main scientific difficulty in achieving a controlled fusion process is the A) very large number of gamma rays emitted. B) very large number of positrons emitted. C) enormous repulsion between the electrons of atoms being fused. D) very large number of x-rays emitted. E) enormous repulsion between nuclei being fused.

E

The more __________ the value of E°red, the greater the driving force for reduction. A) negative B) extensive C) endothermic D) exothermic E) positive

E

The standard cell potential (E°cell) for the reaction below is +0.63 V. The cell potential for this 27) reaction is __________ V when [ Zn2+] = 1.0 M and [Pb2+] = 2.0 × 10-4 M. A) 0.74 B) 0.41 C) 0.85 D) 0.63 E) 0.52

E

A positive number for maximum useful work in a spontaneous process (voltaic cell) indicates that the cell will perform work on its surroundings. True/False

F

The standard reduction potential of X is 1.23 V and that of Y is -0.44 V therefore X is oxidized by Y. True/False

F

The standard reduction potential, E ored , is proportional to the stoichiometric coefficient. True/False

F

In a half reaction the amount of a substance that is reduced or oxidized is directly proportional to the number of electrons generated in the cell. True/False

T