PHY SI Exam 3

What is the charge of iron (Fe) in the compound Fe2O3?

+3

The Second Law of Thermodynamics (Law of Increasing Disorder) places limits on the efficiency of energy conversion. Which of the following is allowed?

100% conversion of electricity to ambient temperature thermal energy

The mass of a chlorine atom in atomic mass units is approximately 35. The atom has

18 neutrons.

Which of the following is a correct and balanced equation showing the reaction of calcium and oxygen? (While several of the equations may be balanced, only one has the correct products and reactants as well as being correctly balanced.)

2Ca + O2 = 2CaO

In which of the following processes is the end product more ordered than the reactants? (In which process does entropy decrease in the system?)

2H2 (gas) + O2 (gas) = 2 H2O (gas)

If the activity of a radioactive substance drops to 1/16 its initial value in 12 hours, what is its half life?

3 hours

Suppose the carbon and oxygen react according to the equation: O2 + 2C = 2CO. If you started with sixty oxygen molecules (60O2) and sixty carbon (60C), how many carbon monoxide molecules could you make?

60

Which of the following is a correct comparison of metals and semiconductors?

A metal's resistance increases when temperature increases while a semiconductor's resistance decreases.

How would the silicate units be connected for the mineral in this picture?

A network of connected silicate molecules extending out in all directions.

Which of the following is not why alloys are useful to us today?

Alloys have a higher conductivity rate.

When you compare the melting point of the 3 molecules what do you find?

B has the lowest melting point

Why are metals opaque?

Because metals have empty, overlapping orbitals for their electrons that create very closely spaced energy levels.

For the reactions shown in the graph for the problem above, which reaction releases the most energy?

C

Which reaction has the highest activation energy?

C

Which of these equations is balanced correctly?

C + O2 = CO2

What happens to the entropy of the universe as the products are formed in an exothermic chemical reaction?

Chemical potential energy is converted into thermal energy resulting in an increase in entropy.

Metals have higher ionization energies than nonmetals do.

False

Quartz, a mineral with no regular pattern when seen in large quantities, has fibrous layering in its atomic structure.

False

Which of the following fatty acids is best for human health?

Fatty acids that have one or more "bent" cis-double bonds between carbon atoms.

Why is a high temperature required for nuclear fusion to occur?

High temperatures are required to allow the nuclei to have enough kinetic energy to overcome the electromagnetic repulsion and have the strong force attraction take place.

Which of the following is a true statement about melting and boiling points in materials made of covalent molecules?

Hydrogen bonding between molecules increases melting and boiling points.

This chart shows electronegativities. What can you conclude about the molecule?

The oxygen will be more negative than the carbon.

When you compare the mass of the products to the mass of the reactants in a fission reaction, what do you find? (Note the question is asking about mass, not mass number.)

The reactants have more mass.

When you compare the band gap for a red and a blue LED, what is true?

The red LED has the smallest band gap.

A window air conditioner is normally placed in a window so the hot air from the back blows outside. What would happen if the air conditioner were placed in the middle of a closed room and turned on?

The room would heat up because all of the energy absorbed by the air conditioner, both thermal and electrical potential, is released back into the room as thermal energy.

Which of the following processes is closest to an ideal reversible process?

an ice cube floating in a glass of water at zero degrees

In which kind of radioactive decay would the number of protons in the resulting nucleus be more than in the initial nucleus?

beta decay

Which of the following is not a characteristic of a metal or alloy?

brittle

Which of these statements best describes the room temperature characteristics of ionic substances?

brittle, non-conducting solid with high melting points

For the Butylene molecule C, what forces would be the largest forces holding one of the molecules to another molecule? (What are the largest intermolecular forces?)

dispersion forces

In order for an energetically favorable chemical reaction to occur

entropy must increase as a result of the reaction.

Which of these sets of properties is most likely those associated with methane, a covalently bonded compound?

gas at room temperature, colorless, does not conduct electricity when solid

Which type of energy is the most ordered?

gravitational potential energy

The primary obstacle to controlled fusion reactions as a source of energy is

overcoming the electromagnetic repulsion of particles with like charges.

Locate the elements palladium (Pd, atomic #46) and nickel (Ni, atomic #28) on the periodic table. If Pd is combined with Ni, which of the following characteristics will the product show at room temperature?

shiny, malleable solid

Here are the common names and contents for a number of common substances. Four are compounds, one is not. Which is not a compound?

sulfur, consisting of molecules having eight S atoms

The process known as nuclear fission is primarily responsible for

the energy produced by a nuclear reactor.

The purpose of the control rods in a nuclear fission reactor is

to absorb neutrons, thus limiting the number of nuclei undergoing fission.

Use the periodic table to decide if S is a metal or a nonmetal. Do the same for O. If these two form a compound, which of these characteristics will it show at room temperature?

transparent gas

A refrigerator causes a transfer of thermal energy from a cooler region to a hotter region. The separation of hot and cold causes an increase in order. The following two questions deal with this situation.

If the refrigerator door was left open, the temperature of the room will increase. This is because the refrigerator will transfer heat from a cooler region (inside the refrigerator) to a hotter region (the room). The law of increasing disorder, states that the total entropy of an isolated system will always increase over time. In this case, the system is the room and refrigerator, and leaving the door open allows the thermal energy to flow freely between both regions, increasing the disorder of the system.

In an irreversible process, what happens to the overall disorder of the universe?

It increases.

Which of the following correctly applies the law of increasing disorder to an air conditioner?

It is true that the heat flow from the cold region to the hotter region increases order, but this is made up for by increasing the disorder of energy from another source.

How does a catalyst affect a reaction?

It lowers the activation energy.

Which of the following are most chemically similar to Pd?

Ni and Pt

If the fridge door were shut, order would appear to increase with the separation of hot and cold. Explain how this is possible using the Law of Increasing Disorder.

Order would appear to increase by closing the door because according to the Law of Increasing Disorder this will decrease the amount of entropy or disorder in the room. Because thermal energy is not able to freely roam between the refrigerator and the room the entropy will be lower and therefore more ordered.

The gasoline engine of an automobile is considerably less than 100% efficient. This means that not all of the energy in the gasoline is turned into kinetic energy of the car. Which of these statements best explains why?

Some of the chemical potential energy in the gasoline must become ambient thermal energy if the rest is to supply the kinetic energy of the automobile. This means some energy must be wasted.

Sugar is a covalent molecule that is solid at room temperature and dissolves easily in water. What does this information tell us about the molecule?

Sugar molecules are polar.

What can you determine from the graph?

The individual proton's and neutron's mass is smallest for atoms with a mass of about 50, and larger for atoms with very small or very big mass.

SHORT ANSWER ON EXAM!!!! On the exam you will have two short essay questions. One of the topics will be on the information in Reconsidering the Risks of Nuclear Power, an article comparing nuclear energy with other forms of energy, and in these three videos: Nuclear Energy Explained: How does it work? 1/3 3 Reasons Why Nuclear Energy Is Terrible! 2/3 3 Reasons Why Nuclear Energy Is Awesome! 3/3 Please review read/listen these article and videos and answer the following two questions: What is the best description of the tools that scientists used to find answers in the coal plant versus nuclear plant debate? How does the article suggest mitigating the dangers of nuclear power?

Scientists used percentage of global energy supply to find the answers they needed in determining coal vs nuclear plants. They posed the question that are all of these disasters worth risking again if we are only producing 10% of the global energy. Additionally, they looked at the amount of greenhouse gases produced by coal plants compared to nuclear plants and found that about 64 giga tonnes of greenhouse gases have not been pumped out since 1976 because of these nuclear plants. They also looked at the death toll that nuclear plants have on the world and found that it saves lives. Studies showed that around 1.8 million deaths had been prevented between 1976 and 2009. The article suggests that we can mitigate the dangers of nuclear power by attempting to locate a proper waste disposal for the large amounts of radioactive uranium to not harm our environment. The article also discusses alternative nuclear technology like the thorium reactor (which we haven't done that much research on) that could solve all of nuclear problems. They discuss that it is much harder to turn thorium into nuclear weapons, that it is extremely abundant, and up to two orders of magnitude less wasteful than current nuclear reactors. In terms of efficiency, 1 tonne of thorium can produce the same amount of energy as 200 tonnes of uranium and 3,500,000 tonnes of coal.

A refrigerator is normally run with its door closed. What would happen if the refrigerator were placed in the middle of a closed room with its door open and turned on?

The room would heat up because all of the energy absorbed by the refrigerator, both thermal and electrical potential, is released back into the room as thermal energy.

Which of these statements correctly describes the ranges of forces between charged nucleons in nuclear physics? "Short distances" refers to distances about the size of the diameter of a nucleon.

The strong interaction is stronger than the electromagnetic interaction at short distances, but the reverse is true at sufficiently long distances.

Carbon-14 (614C) is not stable and it spontaneously decays into nitrogen-14 (714N) and an electron by a radioactive beta-decay. Which of the following is true about the decay?

The total number of nucleons stays the same.

Although fusion is preferred, why are all commercial nuclear power plants using energy from fission instead of energy from fusion?

There are technical challenges to move things commercial with fusion reactors. The conditions required to achieve fusion are extremely difficult to maintain over love periods of time. Another factor is cost. Developing a fusion reactor is a significant investment in research and development, and the technology is not yet mature enough. Regulatory issues are also a concern, where the idea of nuclear plants being placed around are still a bit taboo. Which adds to the difficulty to get funding. Most of our infrastructure is already supporting fission so it is a difficult ask to switch over with all of these negatives in the way.

What best describes how the oxygen molecules would behave if mixed with water?

They would dissolve poorly or not at all because they are not polar.

How do semiconductors change with increasing temperatures?

When you heat them up, semiconductors act more like metals.

Which of the following would best describe the room temperature characteristics of the substance that results from the reaction between magnesium (Mg) and oxygen (O)?

a brittle, transparent, electrically non-conducting solid

Which of these statements best describes a metal?

a network solid consisting of positively-charged atoms in a sea of electrons

Which of the following would best describe the characteristics of the material formed?

a non-conducting material with low melting and boiling points, likely liquid or gas at room temperature.

Which of these processes is closest to an ideal reversible process?

a pendulum swinging with almost no friction

If carbon is combined with oxygen, it forms a new molecular material. The next five questions ask you to make some predictions about the characteristics and behavior of this molecule. What type of bond would exist between the carbon and the oxygen?

covalent

Uranium-238 alpha decays, emitting a helium-4 nucleus. What is the mass number of the product?

234

What happens to the valence electrons as the product (MgO) is formed?

The magnesium atoms' valence electrons are effectively transferred to oxygen.

Which of these is a saturated hydrocarbon?

Saturated fats do not contain double bonds (double line thingy)

When you compare saturated with unsaturated fatty acids containing the same number of carbon atoms, what is true?

Saturated fatty acids have more hydrogen atoms.

Both fission and fusion can result in a release of energy. Why?

The nuclei of atoms near the middle of the periodic table have the least energy and the nucleons with the smallest mass. The difference in mass is converted into energy.