ENGCHEM EF1 EXAM TWO (March 18, 2025)
Due Mar 18 at 2:15pm
Points 30
Questions 30
Available Mar 18 at 1:15pm - Apr 10 at 10:30am
Time Limit 60 Minutes
Instructions
During the conduct of the examination, students are not allowed to do the following:
1. communicate with another examinee during the exam
2. borrow anything from another examinee
3. use mobile phones or other unauthorized gadgets
4. refer to personal notes or access online materials
5. leave the examination room without prior permission from the proctor, or in general,
6. commit academic misconduct/dishonesty particularly as defined by the DLSU student
handbook
7. Results will be invalidated if you are unable to begin within 5 mins from the start
of the exam.
8. Your exam results are valid only if you have signed the attendance sheet in person
during the exam.
Upon the start of the test, examinees may communicate ONLY with the proctor.
In multiple choice questions, SELECT THE BEST ANSWER.
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This quiz was locked Apr 10 at 10:30am.
Attempt History
LATEST
Attempt
Time
Score
Attempt 1
21 minutes
26 out of 30
 Correct answers are no longer available.
Score for this quiz: 26 out of 30
Submitted Mar 18 at 1:36pm
This attempt took 21 minutes.
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Question 1
1 / 1 pts
Which of the following statements is/are correct?
A. Nuclear chemistry focuses on the reactions and properties of atomic nuclei, distinct from
traditional chemistry that deals with electron interactions.
B. Some atomic nuclei are unstable and spontaneously emit radiation to achieve stability.
This process is known as radioactivity.
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C. Alpha (α) Particles consist of one proton and two neutrons
D. All of these
A and B
C
D
A and C
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IncorrectQuestion 2
0 / 1 pts
In 1896, French physicist Henri Becquerel made a groundbreaking discovery that laid the
foundation for our understanding of radioactivity. Building upon Wilhelm Röntgen's discovery
of X-rays in 1895, Becquerel investigated whether phosphorescent materials could emit
similar penetrating rays. He conducted experiments using potassium uranyl sulfate, a
uranium-containing compound, which he placed on photographic plates wrapped in black
paper to block light. Becquerel hypothesized that exposure to sunlight would cause the
uranium to emit X-rays, which the photographic plates would then detect.
However, due to overcast weather, Becquerel stored the prepared materials in a dark
drawer, postponing the experiment. To his surprise, upon developing the photographic
plates later, he observed that they had been fogged, even though they had not been
exposed to sunlight. This unexpected result led Becquerel to realize that the uranium salts
emitted radiation spontaneously, without the need for an external energy source like
sunlight.
Uranium undergoes alpha decay.
Which is correct?
A. Alpha particles are identical to the hydrogen nucleus
B. The mass number of alpha particles is 4
C. A and B
D. A only
B
A
C
D
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Question 3
1 / 1 pts
An isotope of uranium is given the notation
How many protons and neutrons are there in the nucleus of this isotope?
A. 92 protons and 146 neutrons
B. 92 neutrons and 146 protons
C. 238 neutrons and 92 protons
D. 238 protons and 92 neutrons
A
B
C
D
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Question 4
1 / 1 pts
A nuclear equation symbolically represents a nuclear reaction, detailing the transformation
of atomic nuclei during processes like radioactive decay, fission, or fusion. It specifies the
original nuclides (reactants), the resulting nuclides (products), their respective mass
numbers (total number of protons and neutrons), atomic numbers (number of protons), and
any other particles involved, such as alpha particles, beta particles, or gamma rays. . For
example,
Which is correct about the above?
A. it describes a fusion reaction
B. it describes a fission reaction
C. the equation is not balanced
D. all of these
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B
A
C
D
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Question 5
1 / 1 pts
How do U-238 and U-234 compare in terms of the number of protons and the number of
neutrons?
A. The U-238 nucleus has 238 neutrons
B. The U-238 nucleus has more protons than that of U-234
C. U-238 and U234 have equal number of protons
D. A and B only
C
A
B
D
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Question 6
1 / 1 pts
Which is correct?
A. TNT stands for tetranitrotoluene
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B. 2.0 kg of U-235 is equivalent to 40,000,000 kg of TNT
C. Joule is a unit of mass
D. 1.0 kg of TNT is equivalent to 22,000 tons of U-235
B
A
C
D
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Question 7
1 / 1 pts
A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and
sustained at a steady rate (as opposed to a nuclear explosion, where the chain reaction
occurs in a split second).
Which of the following are found within the containment dome of a nuclear reactor (see
above diagram)
A. cooling tower
B. body of water C. fuel rods D. control rods
C and D
A and B
C only
D only
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Question 8
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1 / 1 pts
Which of the following involves transmutation?
A, B, C
A, B, C, D
A and B only
E
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Question 9
1 / 1 pts
An atom consists of a nucleus at the center and electrons on the outside in atomic orbitals.
Nuclei are composed of protons and neutrons. Which of the following is correct?
A. The actual mass of the nucleus is less than the sum of individual masses of neutrons
and protons which constitute it. This difference is called mass defect.
B. The difference between the combined mass of the individual nucleons (protons and
neutrons) and the actual nuclear mass is known as the mass defect. It corresponds to the
binding energy that holds the nucleus together.
C. Nuclear binding energy is the energy released in the formation of a complete atom from
protons, neutrons, and electrons.
D. All of these
A and B
C
D
B
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Question 10
1 / 1 pts
In France, renewable energy accounted for 27% of electricity consumption in 2020 (source:
RTE). Although this figure is a record high, it remains low. On February 10, 2022, President
Macron announced that he intended to double the production of electricity from
renewable sources by 2030 and "increase it still further by 2050". The France 2030 plan
will see 1 billion euros dedicated to innovation in renewable energy.
Which of the following is correct ?
A. Renewable energy sources are naturally replenishing resources that provide sustainable
alternatives to fossil fuels.
B. Solar Energy systems capture sunlight using photovoltaic cells or solar thermal systems
to generate electricity or heat.
C. Wind Energy systems utilize wind turbines to convert the kinetic energy of wind into
electricity.
D. Hydropower generates electricity by harnessing the energy of flowing water
E. All of these
E
A, B
B, C
D
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Question 11
1 / 1 pts
Which of the following best describes first-order nuclear decay?
A. The decay rate is constant over the course of the reaction.
B. The decay rate is proportional to the square root of the number of undecayed nuclei.
C. The decay rate is independent of the number of undecayed nuclei.
D. The decay rate is directly proportional to the number of undecayed nuclei.
D
A
B
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C
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Question 12
1 / 1 pts
The half-life of a radioactive isotope is 10 hours. What fraction of the original sample
remains after 30 hours?
A. 1/2
B. 1/4
C. 1/8
D. 1/16
C
B
A
D
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Question 13
1 / 1 pts
The half-life of a radioactive substance is the time required for half of its unstable nuclei to
undergo radioactive decay, transforming into more stable forms. This characteristic time
interval is unique to each radioisotope and can vary widely—from fractions of a second to
billions of years—depending on the stability of the nucleus. Understanding half-life is crucial
in fields such as radiometric dating, nuclear medicine, and radiation safety, as it helps
predict the behavior and longevity of radioactive materials.
A certain radioactive isotope decays to 12.5% of its original activity in 6 hours. What is its
half-life?
A. 2 hours
B. 3 hours
C. 4 hours
D. 6 hours
A
B
C
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D
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Question 14
1 / 1 pts
The half-life of a radioactive substance is the time required for half of its unstable nuclei to
undergo radioactive decay, transforming into more stable forms. This characteristic time
interval is unique to each radioisotope and can vary widely—from fractions of a second to
billions of years—depending on the stability of the nucleus. Understanding half-life is crucial
in fields such as radiometric dating, nuclear medicine, and radiation safety, as it helps
predict the behavior and longevity of radioactive materials.
The half-life of a radioactive isotope can be written as
t1/2 = Ln 2 / k
where k is the reaction rate constant
Which is True?
A. Nuclear reactions with very large rate constants have short half-lives
B. nuclear reactions with very large rate constants have long half-lives
C. nuclear reactions with very small rate constants have short half-lives
D. None of these
A
B
C
D
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Question 15
1 / 1 pts
Which international agreement aims to phase out the production and consumption of
ozone-depleting substances, including CFCs?
A. Kyoto Protocol
B. Paris Agreement
C. Montreal Protocol
D. Vienna Convention
C
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A
B
D
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Question 16
1 / 1 pts
Certain compounds are blamed for the depletion of the ozone layer. Which of the following
is correct?
A. CO2 traps heat by absorbing ultraviolet radiation and causing the rise in global
temperature
B. Chlorofluorocarbons or CFC's release chlorine atoms that destroy ozone molecules
C. CFC's increase greenhouse gas concentrations
D. CFC's reflect solar radiation into space
B
A
C
D
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Question 17
1 / 1 pts
Earth's atmosphere is a vital layer of gases encircling the planet, sustained by gravitational
forces. This gaseous envelope is predominantly composed of nitrogen (approximately 78%)
and oxygen (about 21%), with minor constituents like argon (around 0.93%) and carbon
dioxide (approximately 0.04%). Additionally, water vapor is present in variable quantities,
averaging around 1% at sea level.
The atmosphere is stratified into distinct layers based on temperature gradients and other
characteristics.
Which layer of the atmosphere is closest to Earth's surface and is where most weather
phenomena occur?
A. Stratosphere
B. Mesosphere
C. Troposphere
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D. Thermosphere
C
A
B
D
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Question 18
1 / 1 pts
Which of the following describes the stratosphere?
A. Extending from Earth's surface up to about 8 to 15 kilometers, this layer contains
approximately 75% of the atmosphere's mass and is where most weather phenomena
occur.
B. Situated above the troposphere, extending up to about 50 kilometers, it houses the ozone
layer, which absorbs and scatters ultraviolet solar radiation.
C. Ranging from 50 to 85 kilometers above the surface, this layer is where most meteors
burn upon entering Earth's atmosphere.
D. Extending from 85 to 600 kilometers, it contains the ionosphere, a region important for
radio communication due to its ionized particles.
B
A
C
D
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Question 19
1 / 1 pts
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Single nuclear reactors typically have a maximum power capacity between
____________________.
A typical coal-fired power plant generates electricity at a rate of 600 MW.
500 and 1300 MW
50 and 130 MW
500 and 1300 KW
5000 and 13,000 MW
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Question 20
1 / 1 pts
They are a part of the electromagnetic spectrum, with more energy (shorter wavelength)
than X-rays.
The particle has zero charge.
In nuclear decay, the nucleus that emits them does not change either the mass number or
the atomic number.
gamma rays
UV rays
Visible light
photon
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Question 21
1 / 1 pts
The Greenhouse effect is used to explain certain global phenomena.
Which of the following is true ?
A. The greenhouse effect is a natural phenomenon where specific gases in Earth's
atmosphere, known as greenhouse gases, trap heat, preventing it from escaping into space
and thereby warming the planet.
B. The primary greenhouse gases include carbon dioxide, methane, nitrous oxide, ozone,
and water vapor.
C. This effect is essential for maintaining Earth's average temperature at a habitable level,
making life possible.
D. All of these
D
A
B
C
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IncorrectQuestion 22
0 / 1 pts
Chernobyl: What Happened?
Fifty different radioactive isotopes were released, with half-lives spanning from two hours to
24,000 years. These isotopes were shot 1.5 miles into the sky. One of the hazardous
radioisotopes released was iodine-131, If ingested, this radioisotope can cause thyroid
cancer.
Which of the following is correct?
A. I-131 is a beta emitter
B. The decay of I-131 produces gamma rays
C. The Chernobyl nuclear plant did not have a containment dome.
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D. All of these
D
A
B
C
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Question 23
1 / 1 pts
The commercial synthesis of ammonia is primarily achieved through a method that was
developed in the early 20th century. This process synthesizes ammonia (NH₃) by directly
combining nitrogen (N₂) from the air with hydrogen (H₂) derived mainly from natural gas
(methane). This process is known as the
A. Greenhouse effect
B. Montreal Protocol
C. Haber-Bosch process
D. Bosch Reaction
E. Manhattan project
C
A
B
D
E
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Question 24
1 / 1 pts
The transformation of nitrogen gas is a natural process that converts atmospheric nitrogen
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(N₂) into biologically usable forms, such as nitrates and ammonia, which are essential for
plant growth. This process is induced by lightning. Lightning generates extremely high
temperatures, reaching up to 30,000 Kelvin. This intense heat provides the energy
necessary to break the strong triple bonds of nitrogen molecules (N₂), enabling nitrogen
atoms to react with oxygen (O₂) in the atmosphere, forming nitrogen oxides (NOₓ).
While lightning-induced reaction of nitrogen contributes to soil fertility, it accounts for a
relatively small portion of the total nitrogen fixed annually. The majority is performed by
specialized bacteria through biological processes.
This natural mechanism exemplifies how atmospheric phenomena like lightning play a
crucial role in nutrient cycling and ecosystem sustainability.
The conversion of molecular nitrogen (N2) into nitrogen compounds where atmospheric
nitrogen gas is converted into nitrates and other compounds suitable for assimilation by
algae and plants is called __________________.
A. Ozone layer
B. Nitrogen fixation
C. greenhouse gas
D. Montreal protocol
B
A
C
D
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Question 25
1 / 1 pts
These are violent eruptions on the surface of the sun that emit electrons and protons
towards space, leading to disruption in radio transmission and the auroras. It involves a
sudden, intense burst of electromagnetic radiation originating from the Sun's atmosphere.
These occur when energy stored in 'twisted' magnetic fields, usually above sunspots, is
suddenly released. This release heats material to many millions of degrees in just a few
minutes and produces a burst of radiation across the electromagnetic spectrum, from radio
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waves to X-rays and gamma rays
These refer to
A. Solar flares
B. Greenhouse effect
C. Tidal power
D. Montreal protocol
A
B
C
D
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Question 26
1 / 1 pts
Various processes occur in the atmosphere which affect climate. Which of the following is
correct?
A.. The greenhouse effect is a natural process that warms Earth's surface.
B. When the Sun's energy reaches Earth, some of it is reflected back to space, and the
rest is absorbed, warming the planet. Earth then emits this energy as heat (infrared
radiation).
C. Greenhouse gases in the atmosphere—such as carbon dioxide (CO₂), methane (CH₄),
nitrous oxide (N₂O), ozone (O₃), and water vapor—trap some of this heat, preventing it from
escaping into space.
D. The greenhouse effect is responsible for maintaining Earth's average temperature at a
habitable level, making life possible.
E. All of these
E
A
B
C
D
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IncorrectQuestion 27
0 / 1 pts
An internal combustion engine (ICE) is a type of heat engine where the combustion of fuel
occurs within the engine itself, converting chemical energy into mechanical energy. This
process involves igniting a fuel-air mixture inside a combustion chamber, producing
expanding gases that move mechanical components, ultimately generating power.
The most common type of ICE is the four-stroke engine, which operates through four distinct
phases:
1. Intake Stroke: The intake valve opens, and the piston moves downward, allowing a
combustible mixture to enter the combustion chamber.
2. Compression Stroke: The intake valve closes, and the piston moves upward,
compressing the mixture to increase its potential energy.
3. Power (Combustion) Stroke: A spark plug ignites the compressed combustible mixture,
causing an explosion that forces the piston downward, producing mechanical work.
4. Exhaust Stroke: The exhaust valve opens, and the piston moves upward again, expelling
the combustion gases from the chamber.
Which is correct?
A. ICE's use air as a source of oxygen necessary for the combustion to occur. The
combustible mixture is an air-fuel mixture.
B. The nitrogen in the air may react with O2 to form nitrogen oxides.
C. The combustion cannot occur without nitrogen
D. All of these
A and B
D
B only
C only
B and C
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IncorrectQuestion 28
0 / 1 pts
By filtering out the majority of the Sun's harmful UV radiation, the stratosphere's ozone layer
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acts as Earth's "sunscreen," safeguarding living organisms from potential damage.
Human activities have led to the emission of ozone-depleting substances, causing thinning
of this protective layer. However, international efforts to phase out these substances have
been successful, and the ozone layer is on a path to recovery.
Understanding the stratosphere's role in shielding life from solar radiation underscores the
importance of preserving this vital component of our atmosphere.
Which is true?
A. Ozone absorbs UV radiation leading to its dissociation back into molecular oxygen
B. Ozone can react with certain chemicals known as ozone depleting substances. This led
to the decrease on ozone concentration in the stratosphere
C. Ozone is a pollutant when found in the troposphere
D. All of these
D
A
B
C
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Question 29
1 / 1 pts
It is a landmark international treaty designed to protect the Earth's ozone layer by phasing
out the production and consumption of numerous substances responsible for ozone
depletion. Adopted on September 16, 1987, and entering into force on January 1, 1989, it
has achieved universal ratification by all 198 United Nations member countries, making it
one of the most successful environmental agreements in history.
The agreement targets nearly 100 man-made chemicals, including chlorofluorocarbons
(CFCs) and halons, which were commonly used in refrigeration, air conditioning, and
aerosol propellants. By regulating and reducing the use of these substances, it aims to allow
the ozone layer to recover.
It has been updated multiple times to include new scientific findings and to address
additional substances. Notably, the 2016 Kigali Amendment aims to phase down
hydrofluorocarbons (HFCs), potent greenhouse gases used as replacements for earlier
banned substances.
Thanks to global adherence to the, the ozone layer is on the path to recovery. Projections
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indicate that it will return to 1980 levels by 2040 over most of the world, by 2045 over the
Arctic, and by 2066 over Antarctica.
The "agreement" is called:
A. Montreal Protocol
B. Kyoto Protocol
C. United Nations
D. Paris Agreement
A
B
C
D
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Question 30
1 / 1 pts
Not all countries agree to implement steps that will reduce CO2 emissions.
What are the reasons?
A. Nations rich in fossil fuel resources, such as oil, coal, or natural gas, often rely heavily on
their extraction and export for economic stability. Transitioning away from these industries
could lead to significant economic challenges, including job losses and reduced national
revenue.
B. Developing countries may prioritize economic growth and poverty alleviation over
stringent emission reductions. They argue that industrialized nations, having historically
contributed more to greenhouse gas emissions, should shoulder a greater responsibility for
mitigation efforts.
C. Some countries fear that reducing CO₂ emissions could compromise their energy
security. Dependence on renewable energy sources, which can be intermittent, might not
yet provide the reliability needed to meet their energy demands consistently.
D. All of these
D
A
B
C
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Quiz Score: 26 out of 30
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