EXAM 4

Question 1

Reduction is the

gain of electrons.
loss of electrons.
gain of protons.
loss of protons.
loss of mass.

Question 2

Oxidation is the

gain of electrons.
loss of electrons.
gain of protons.
loss of protons.
loss of mass.

Answer 2

loss of electrons

Question 3

What is the oxidation number of chromium in the ionic compound ammonium dichromate, (NH4)2Cr2O7?

+3
+4
+5
+6
+7

Answer 3

+6

Question 4

On a periodic table, where do you expect to find elements that are good oxidizing agents?

on the right (except for the last group)
in the middle left
in the top left
at the bottom
in the transition metals

Answer 4

on the right (except for the last group)

Question 5

Where in the periodic table do you find the elements that are the best reducing agents with the most negative standard reduction potentials?

in group 16
on the left
in the middle
at the bottom
in group 17

Answer 5

on the left

Question 6

Applying a current to a rechargeable battery converts it from ________ cell to ________ cell.

a voltaic; an electrolytic
an electrolytic; a voltaic
a Leclanché; a Nernst
a Nernst; a Leclanché
a Born cell; a Haber

Answer 6

a voltaic; an electrolytic

Question 7

Which statement is correct about a voltaic cell?

The electron flow in the external circuit is from the positive electrode to the negative electrode.
The electron flow in the external circuit is from the cathode to the anode.
Electrons are transferred from the oxidizing agent to the reducing agent.
Chemical energy is transformed into electrical energy by a spontaneous redox reaction.
Positive ions diffuse through a porous bridge from the cathode compartment to the anode compartment.

Answer 7

Chemical energy is transformed into electrical energy by a spontaneous redox reaction.

Question 8

Which statement about an anode in a voltaic cell is correct?

Oxidation occurs at the anode.
Reduction occurs at the anode.
Usually, the cathode is a dissolved ion.
In the external circuit, electrons flow toward the anode.
Chemical species can have their oxidation numbers decreased at the anode.

Answer 8

Oxidation occurs at the anode.

Question 9

The electrodes on batteries are labeled + and -. The ________ is labeled ________, and ________ occurs there.

anode; positive; oxidation
anode; negative; reduction
cathode; positive; reduction
cathode; negative; reduction
cathode; positive; oxidation

Answer 9

cathode; positive; reduction

Question 9

The electrodes on batteries are labeled + and -. The ________ is labeled ________, and ________ occurs there.

anode; positive; oxidation
anode; negative; oxidation
cathode; positive; oxidation
cathode; negative; reduction
anode; positive; reduction

Answer 9

anode; negative; oxidation

Question 10

This diagram represents a voltaic cell. In this cell, which species is oxidized?

Cd(s)|Cd2+ (aq)||Fe3+ (aq),Fe2+ (aq)|Pt(s)

Cd(s)
Cd2+ (aq)
Fe2+ (aq)
Fe3+ (aq)
Pt(s)

Answer 10

Cd(s)

Question 11

This diagram represents a voltaic cell. In this cell, which species is reduced?

Zn(s)|Zn2+ (1.0 M)||Cu2+ (1.0 M)|Cu(s)

Zn(s)
Zn2+ (aq)
Cu2+ (aq)
Cu(s)
C(s)

Answer 11

Cu2+ (aq)

Question 12

This diagram represents a voltaic cell. What is the balanced electrochemical reaction represented by this cell?

Al(s)|Al3+ (1.0 M)||Cu2+ (1.0 M)|Cu(s)

2Al(s) + 3Cu2+(aq) 2Al3+(aq) + 3Cu(s)

2Al3+(aq) + 3Cu(s) 2Al(s) + 3Cu2+(aq)

Answer 12

2Al(s) + 3Cu2+(aq) 2Al3+(aq) + 3Cu(s)

Question 13

This diagram represents a voltaic cell. In this cell, which species is the oxidizing agent?

Al(s)|Al3+ (1.0 M)||Cu2+ (1.0 M)|Cu(s)

Cu2+ (aq)
Cu(s)
Al(s)
Al3+ (aq)
Pt(s)

Answer 13

Cu2+ (aq)

Question 14

If the potential of a voltaic cell is +1.20 V, what is the free-energy change when one mole of electrons is transferred in the oxidation–reduction reaction?

116 kJ
1.20 kJ
-1.20 kJ
-116 kJ
+602 kJ

Answer 14

-116 kJ

Question 15

If the potential of a voltaic cell is +0.837 V, what is the free-energy change when two moles of electrons are transferred in the oxidation–reduction reaction?

+162 kJ
-162 kJ
-82.0 kJ
+82.0 kJ
+41.0 kJ

Answer 15

-162 kJ

Question 16

The spontaneous redox reaction in a voltaic cell has

a negative value of Ecell and a negative value of ΔG.
a positive value of Ecell and a positive value of ΔG.
a negative value of Ecell and a positive value of ΔG.
a positive value of Ecell and a negative value of ΔG.
a positive value of Ecell and a value of zero for ΔG

Answer 16

a positive value of Ecell and a negative value of ΔG.

Question 17

The standard hydrogen electrode is

used to calibrate voltmeters.
used to produce a set of standard reduction potentials.
needed to activate electrochemical cells.
often overlooked in measuring standard reduction potentials.
used to produce a standard cell potential of exactly 1 V.

Answer 17

used to produce a set of standard reduction potentials.

Question 18

The Nernst equation can be used to calculate

standard cell potentials from standard reduction potentials.
the change in standard Gibbs free energy from standard cell potentials.
cell potentials from standard cell potentials when the conditions of concentration and temperature are not standard.
cell potentials given the temperature and reactant concentrations.
cell potentials from standard oxidation potentials.

Answer 18

cell potentials from standard cell potentials when the conditions of concentration and temperature are not standard.

Question 19

A concentration cell is constructed by using the same half-reaction for both the cathode and anode. What is the value of standard cell potential, , for a concentration cell that combines a silver anode in contact with 0.10 M silver nitrate and a silver cathode in contact with 0.00003 M silver nitrate? ( Ered=+0.80 V for Ag/Ag+)

-0.21 V
0.00 V
+0.80 V
-0.80 V
+0.21 V

Answer 19

0.00V

Question 20

Which statement correctly describes a “dead” battery with a voltage of 0?

The free-energy change for the reaction now is < 0.
All the reactants have been converted into products.
The products and reactants now are in equilibrium.
Q<K
cell potential < 0

Answer 20

The products and reactants now are in equilibrium.

Question 21

What is true when a battery (voltaic cell) is dead?

Ecell= 0 and Q=K
Ecell= 0 and Q=K
Ecell= 0 and Q= 0
Ecell = 0 and Q= 0
Ecell= 0 and K= 0

Answer 21

Ecell= 0 and Q=K

Question 22

A concentration cell is constructed by using the same half-reaction for both the cathode and anode. What is the value of Ecell for a concentration cell that combines silver electrodes in contact with 0.10 M silver nitrate and 0.00003 M silver nitrate solutions? ( Ered=+0.80 V for Ag/Ag+)

+0.21 V
+0.59 V
+0.80 V
-0.21 V
+1.01 V

Answer 22

+0.21V

Question 23

A typical 1.5 V AAA battery has a capacity of 1 ampere-hour (A × hr.). How much energy can such a battery supply?

5400 J
1.5 J
3600 J
1800 J
90 J

Answer 23

5400 J

Question 24

A typical hearing aid battery has a capacity of 5 ampere-hour (A × hr.) and can supply up to 23.4 kJ of energy. What is the voltage of the battery?

78 V
1.3 V
1.3 × 10-3 V
7.8 × 10-3 V
0.90 V

Answer 24

1.3 V

Question 25

What is the mass of copper used if it was oxidized to copper(II) over 35.0 s, given the average electrical current delivered was 200. A?

1.02 × 10-1 g
1020 g
2.30 g
4.60 g
1.00 g

Answer 25

2.30 g

Question 26

If, in using a lead-acid battery to start a car, 1.00 g of Pb is consumed on the anode, how long will it take to recharge the battery, using a current of 0.500 A, and turn the PbSO4 that was produced back into Pb?

15.5 min
1864 min
31.1 min
21.2 min
42.4 min

Answer 26

31.1 min

Question 27

The unit of current, ampere (A), is defined as

1 C.
1 C/s.
1 mol of electrons.
1 mol of electrons per second.
96,500 C/s.

Answer 27

1 C/s.

Question 28

The unit of electrical power, watt (W), is defined as

1 C.
1 V.
1 J.
1 C V.
1 C V/s.

Answer 28

1 C V/s.

Question 29

1.0 kilowatt hour =

1000 J.
6000 J.
3600 kJ.
3600 J.
6000 kJ.

Answer 29

3600 kj.

Question 30

The peak in nuclear binding energy occurs for an isotope of

helium.
iron.
uranium.
carbon.
lead.

Answer 30

iron.

Question 31

Light elements with Z< 20 generally have a neutron/proton ratio about equal to

0.5.
0.8.
1.0.
1.3.
1.5.

Answer 31

1.0.

Question 32

The most naturally abundant nuclides are those that

have an odd number of protons and an odd number of neutrons.
have an even number of protons and an even number of neutrons.
have noble gas configurations of electrons.
can be produced by fission reactions.
can be produced by fusion reactions.

Answer 32

have an even number of protons and an even number of neutrons.

Question 33

All elements with Z> 83 are

synthetic.
produced by nuclear fission.
radioactive.
not found in nature.
unreactive.

Answer 33

radioactive.

Question 34

Which of the following nuclides (carbon-14, sodium-24, silicon-26, aluminum-27, and/or phosphorus-31) are most likely to be unstable because they have too many neutrons?

only carbon-14
only carbon-14 and sodium-24
only sodium-24 and silicon-26
only silicon-26, aluminum-27, and phosphorus-31
all of these

Answer 34

only carbon-14 and sodium-24

Question 35

Which of the following nuclides (nitrogen-15, boron-8, oxygen-18, fluorine-19, and/or magnesium-28) are most likely to be unstable because they have too many neutrons?

only nitrogen-15 and boron-8
only boron-8 and oxygen-18
only oxygen-18 and fluorine-19
only oxygen-18, fluorine-19, and magnesium-28
all of these

Answer 35

only oxygen-18 and fluorine-19

Question 36

What particle is emitted when iodine-137 decays to xenon-137?

α particle
neutron
proton
positron
β particle

Answer 36

β particle

Question 37

Which process converts a neutron into a proton?

beta emission
positron emission
electron capture
alpha emission
gamma emission

Answer 37

beta emission

Question 38

Positron emission is associated with

the conversion of a neutron to a proton.
the conversion of a proton to a neutron.
an increase in mass number.
a decrease in mass number.
the emission of γ rays.

Answer 38

the conversion of a proton to a neutron

Question 39

Nitrogen-13 decays by positron emission to produce

carbon-13.
oxygen-17.
boron-11.
carbon-14.
boron-13.

Answer 39

carbon-13.

Question 40

Thallium-206 decays by β decay to produce

gold-202.
lead-206.
polonium-209.
mercury-206.
platinum-208.

Answer 40

lead-206.

Question 41

Curium-242 (Cm-242) decays by α decay to produce

plutonium-242.
uranium-240.
berkelium-242.
californium-238.
plutonium-238.

Answer 41

plutonium-238.

Question 42

The activity of a radioactive sample is the number of decay events per second. The SI unit of activity is the becquerel (1 Bq = 1/s). An older unit for activity is the curie (1 Ci = 3.70 × 1010/s). What is the activity in Bq of a sample with an activity of 47 μCi of radiation?

7.9 × 102 Bq
7.9 × 108 Bq
1.7 × 1012 Bq
1.7 × 106 Bq
1.3 × 10-16 Bq

Answer 42

1.7 × 106 Bq

Question 43

The activity of a radioactive sample is the number of decay events per second. The SI unit of activity is the becquerel (1 Bq = 1/s). An older unit for activity is the curie (1 Ci = 3.70 × 1010/s). What is the activity in μ Ci of a sample with an activity of 2.1 × 105 Bq of radiation?

7.8 × 109μCi
5.7 μCi
5.7 × 10-12μCi
5.7 × 10-6μCi
0.21 μCi

Answer 43

5.7 μCi

Question 44

A person’s body generates about 0.2 μCi of radioactivity. Determine the total radioactivity emitted by 300 students in a lecture hall. (1 Ci = 3.7 × 1010 Bq and 1 Bq = 1 decay/s)

2 × 106 decays/s
9 × 1016 decays/s
70 decays/s
2 × 107 decays/s
7 × 103 decays/s

Answer 44

2 × 106 decays/s

Question 45

Radon-222 has a half-life of 3.8 days. A sample from a basement in Colorado was analyzed 5.0 days after it was collected and was found to have an activity of 0.17 Bq. What was the original activity of this sample?

0.22 Bq
0.32 Bq
0.42 Bq
0.62 Bq
0.52 Bq

Answer 45

0.42 Bq

Question 46

Radiation seed therapy is a common method for treating some prostate cancers and brain tumors. Palladium-103, which decays by electron capture and gamma ray emission with a half-life of 17.0 days, is one isotope used for this treatment. How much palladium-103 (102.91 g/mol) is needed to produce an initial radioactivity level of 1.30 mCi? Note: 1 Ci = 3.70 × 1010/s.

0.0174 μg
0.0251 μg
0.0316 μg
0.0995 μg
0.0594 μg

Answer 46

0.0174 μg

Question 47

Radioactive decay is a ________-order process.

zero
first
second
zero or first
zero, first, or second

Answer 47

first

Question 48

Tritium (3H) is used in glowing “EXIT” signs located where there is no electricity for lightbulbs. If the half-life of tritium is 12.26 years, what percentage of the original quantity of the isotope is left in the sign after 18.5 years?

0.632%
63.2%
35.1%
1.51%
25.0%

Answer 48

35.1%

Question 49

Iodine-131 has a half-life of 8.1 days and is used as a tracer for the thyroid gland. If a patient drinks a sodium iodide (NaI) solution containing iodine-131 on a Tuesday, how many days will it take for the concentration of iodine-131 to drop to 5.0% of its initial concentration?

19 days
0.81 day
8.1 days
35 days
4.3 days

Answer 49

35 days

Question 50

Carbon-14 measurements on the linen wrappings from the Book of Isaiah on the Dead Sea Scrolls indicated the scrolls contained about 79.5% of the carbon-14 found in living tissue. Approximately how old are these scrolls? The half-life of carbon-14 is 5730 years.

570 years
820 years
1300 years
1900 years
4600 years

Answer 50

1900 years

Question 51

A 10.00 g sample of wood from an archaeological site produced 3072 β particles in a 10-hour measurement owing to the presence of carbon-14, while a 10.00 g sample of new wood produced 9216 β particles in the same period of time. The half-life of carbon-14 is 5730 years. How old is the wood from the archaeological site?

5730 years
2865 years
4040 years
9080 years
The correct answer differs by more than 100 years from the values given in the answer choices.

Answer 51

9080 years

Question 52

In 2002, a wooden beam from the Wupatki Indian ruins in Arizona was found to contain 235 mg of carbon-14. A sample of wood of the same mass cut sometime in 2002 contained 264 mg of carbon-14. When was the beam from Wupatki cut if the half-life of carbon-14 is 5730 years?

1974 C.E.
750 C.E.
959 C.E..
1042 C.E.
926 C.E.

Answer 52

1042 C.E.

Question 53

A rock from the moon was found to contain 1.0 × 10-5 g of uranium-238 and 4.0 × 10-6 g lead-206. All of the lead-206 came from the decay of uranium-238. The half-life for this decay is 4.5 × 109 years. How old is this rock?

1 × 10^6 years
2 × 10^7 years
4 × 10^8 years
3 × 10^9 years
5 × 10^10 years

Answer 53

3 × 10^9 years

Question 54

Which of the following units is used to quantify the biological effects of radiation?

curies
rems
rads
becquerels
joules

Answer 54

rems

Question 55

The dominant mechanism through which radiation damages biological tissue and living organisms is by

overheating the tissue.
making the tissue radioactive.
directly breaking bonds in DNA.
directly ionizing biological molecules.
ionizing water and producing hydroxy radicals.

Answer 55

ionizing water and producing hydroxy radicals.

Question 56

Which type of radiation does the most tissue damage, but only when the emitter is internally ingested?

alpha
beta
gamma
neutron
positron

Answer 56

alpha

Question 57

Which type of radiation has the greatest penetration ability?

alpha
beta
gamma
neutron
positron

Answer 57

gamma

Question 58

Which type of radiation has the lowest penetration ability?

alpha
beta
gamma
neutron
positron

Answer 58

alpha

Question 59

Cardiac pacemakers once used plutonium-238 as a power source. Plutonium-238 decays by the emission of gamma rays and alpha particles. This emission is not especially harmful because

gamma rays are not absorbed very strongly by biological tissue, and alpha particles do not penetrate beyond the container.
gamma rays and alpha particles are the least dangerous forms of radiation.
gamma rays and alpha particles do not penetrate beyond the container.
gamma rays are absorbed by the container, and alpha particles do not affect biological tissue.
tissue damage caused by gamma rays and alpha particles is rapidly repaired by enzymes.

Answer 59

gamma rays are not absorbed very strongly by biological tissue, and alpha particles do not penetrate beyond the container.

Question 60

Though uranium-238 is radioactive, it can be worked with safely in a glovebox with no additional precautions. This is because

uranium-238 emits gamma rays and they are not absorbed very strongly by biological tissue.
uranium-238 emits alpha particles which are weakly penetrating and do not reach beyond the glovebox.
gamma rays and alpha particles emitted by the uranium-238 do not penetrate beyond the glovebox.
the half-life of uranium-238 is so long that minimal radiation is emitted.
the nitrogen atmosphere of the glovebox inhibits radioactive decay.

Answer 60

uranium-238 emits alpha particles which are weakly penetrating and do not reach beyond the glovebox.

Question 61

Uranium-235 is the fuel in nuclear power plants. When a nucleus of uranium-235 captures a neutron, the nucleus splits into two lighter nuclei and initiates a chain reaction. The chain reaction is driven by the emission of

protons.
neutrons.
positrons.
β particles.
α particles.

Answer 61

neutrons.

Question 62

The major fissionable isotope of uranium used in nuclear power plants is

uranium-238.
uranium-236.
uranium-235.
uranium-234.
uranium-235 and uranium-238.

Answer 62

uranium-235.

Question 63

Electricity is produced from nuclear reactions by

capturing the electrons that are emitted.
accelerating electrons with rapidly moving protons from the nuclear reaction.
a process still not understood by scientists.
using the energy to make steam to turn turbines.
using the energy to accelerate electrons in wires

Answer 63

using the energy to make steam to turn turbines.

Question 64

The purpose of control rods in a fission reactor is to

cool down the reactor fuel.
prevent oxygen from reaching the fuel.
absorb the neutrons generated in the fission process.
absorb the electrons emitted in the fission process.
enhance the neutron capture process.

Answer 64

absorb the neutrons generated in the fission process.

Question 65

A barrel of oil produces about 5.9 × 106 kJ of energy. The fission of 235 g of uranium-235 releases 2.1 × 1010 kJ of energy. How many barrels of oil are equivalent to 1 kg of uranium-235?

3560
15,100
836,600
110,000
55,000

Answer 65

15,100