PHY S100 Sandberg BYU Exam 3 Practice Questions

The purpose of the control rods in a nuclear fission reactor is Select one: A. to slow down the neutrons, since slower neutrons have a higher probability of causing fission. B. to absorb neutrons, thus limiting the number of nuclei undergoing fission. C. to increase the number of neutrons by causing nuclear reactions in the control rods, so that more nuclei in the fuel will undergo fission. D. to act as spacers to keep the fuel elements apart. E. to contain material to be transformed into new fissionable fuel by neutron irradiation.

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

When you compare saturated with unsaturated fatty acids containing the same number of carbon atoms, what is true? Select one: A. Saturated fatty acids have more hydrogen atoms. B. Saturated fatty acids have more oxygen atoms. C. Saturated fatty acids are more curved. D. Saturated fatty acids have lower melting points. E. Saturated fatty acids have more double bonds.

A. Saturated fatty acids have more hydrogen atoms.

In Lesson 20, a magnesium strip was used to ignite the thermite reaction. When magnesium is placed in a flame from a small blow torch, it burns quite brightly forming magnesium oxide, a salt that contains one magnesium for every oxygen. In the following questions you will be asked to provide some details of the chemical processes involved in a reaction between magnesium and oxygen. How many more electrons does unbound oxygen need to fill its 2nd shell? (You may find it helpful to draw the energy well on scratch paper.) Select one. A. 1 B. 2 C. 6 D. 8 E. None, the 2nd shell is full.

B. 2

Uranium-238 alpha decays, emitting a helium-4 nucleus. What is the mass number of the product? Select one: A. 230 B. 234 C. 238 D. 242 E. 246

B. 234

Metals have higher ionization energies than non-metals do. Select one: A. True B. False

B. False

Which type of energy listed below is the most ordered? Select one: A. Nuclear potential energy B. Gravitational potential energy C. Thermal energy D. Chemical potential energy E. Impossible to tell without more information about the process.

B. Gravitational potential energy

What happens to the valence electrons as the product (MgO) is formed? Select one: A. The orbitals spread out into the whole solid and overlap. B. The magnesium atoms' valence electrons are effectively transferred to oxygen. C. The oxygen atoms' valence electrons are effectively transferred to magnesium. D. The orbitals of both atoms' valence electrons change shape so that the electrons are shared equally between the atoms. E. The electrons move to new orbitals that are higher in energy than the individual atomic orbitals.

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

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) Select one: A. The products have more mass B. The reactants have more mass C. The mass is the same on each side

B. The reactants have more mass

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.) A. Ca + O2 = CaO B. Ca + O2 = CaO2 C. 2Ca + O2 = 2CaO D. 4Ca + O2 = 2Ca2O E. Ca + O2 = Ca2O

C. 2Ca + O2 = 2CaO

Which of the following is a mass spectrum for propylene, C3H6? A. a B. b C. c D. d

D. d

Which of the following is NOT why alloys are useful to us today? Alloys Select one: A. have lower melting temperatures. B. have a higher conductivity rate. C. are less malleable. D. reduce weight in objects.

B. have a higher conductivity rate.

In an irreversible process, the overall disorder of the universe Select one: A. is constant. B. decreases. C. increases. D. is zero. E. becomes infinite.

C. increases.

Which of the following tends to have the highest melting and boiling points? Select one: A. Atomic matter B. molecular matter C. network matter

C. network matter

What is the charge of iron (Fe) in the compound Fe2O3? Select one: A. -3 B. -2 C. +2 D. +3

D. +3

How does a catalyst affect a reaction? Select one: A. It raises the activation entropy B. It changes anti-bonding orbitals into bonding orbitals C. It lowers the band gap D. It lowers the activation energy E. It increases the energy of the transition state

D. It lowers the activation energy

Why are metals opaque? Select one: A. because the atoms are closer together than the wavelength of light B. because metals are good heat conductors C. because metals are malleable D. because metals have high melting and boiling points E. because metals have empty, overlapping orbitals for their electrons

E. because metals have empty, overlapping orbitals for their electrons

When you compare the band gap for a red and a blue LED, what is true? Select one: A. The red LED has the smallest band gap. B. The blue LED has the smallest band gap. C. The band gaps are equal as long as the battery powering them is the same. D. The color of light doesn't have anything to do with the band gap.

A. The red LED has the smallest band gap.

Each molecule of nitric acid has the formula HNO33. If there are 6000 oxygen atoms present and 6000 nitrogen atoms present, how many hydrogen atoms will be required to convert all of the oxygen atoms into nitric acid? Select one: A. 1000 B. 2000 C. 4000 D. 6000 E. 18000

B. 2000

In order for a chemical reaction to occur: Select one: A. Energy must decrease as a result of the reaction. B. Entropy must increase as a result of the reaction. C. Energy and entropy must both increase. D. Energy and entropy must both decrease. E. Energy must decrease and entropy must increase.

B. Entropy must increase as a result of the reaction.

In which of the following processes is the end product more ordered than the reactants? (In which process does entropy decrease.) Select one: A. 2H2 (gas) + O2 (gas) = 2 H2O (gas) B. 2C8H18 (liquid) + 25O2 (gas) = 16CO2 (gas) + 18H2O(gas) C. C6H12O6 (solid) + 6O2 (gas) = 6CO2 (gas) + 6H2O (liquid) D. 2C7H5N3O6 (solid) = 3N2(gas) + 7CO(gas) + 5H2O(gas) + 7 C(solid) E. NaHCO3(solid) + C2H4O2(liquid)=C2H3NaO2(solid)+ H2O(liquid) + CO2(gas)

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

The 2nd Law of Thermodynamics (Law of Increasing Disorder) places limits on the efficiency of energy conversion. Which of the following is allowed? Select one: A. 100% conversion of ambient temperature thermal energy to kinetic energy. B. 100% conversion of chemical potential energy to kinetic energy. C. 100% conversion of sunlight to kinetic energy. D. 100% conversion of electricity to ambient temperature thermal energy. E. 100% conversion of ambient temperature thermal energy to chemical potential energy.

D. 100% conversion of electricity to ambient temperature thermal energy.

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? Select one: A. 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. B. The room would heat up because the electrical potential energy loses entropy while the room gains entropy. C. The temperature of the room would stay the same because internal energy is conserved. D. The room would cool down because as the entropy of the electrical potential energy increases, the entropy of the room must decrease to compensate. E. The room would cool down because the electrical potential energy from the outlet decreases the ambient thermal energy in the room.

A. 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.

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? Select one: A. Non-conducting, transparent solid. B. Shiny, malleable solid. C. Transparent gas. D. Brittle, opaque solid. E. Opaque gas.

B. Shiny, malleable solid.

In carbon tetra-chloride, CCl44, what is true about the charge distribution? Select one: A. The carbon will be more negative than the chlorine. B. The chlorine will be more negative than the carbon. C. The chlorine and carbon would be equally negative. D. The atoms will become positive and negative ions. E. It is impossible to predict how the electrons will distribute themselves in this type of bond.

B. The chlorine will be more negative than the carbon.

Which of the following would best describe the characteristics of covalent materials? Select one: A. A brittle, transparent solid with a very high melting point. B. A shiny, malleable solid with a very high melting point. C. A non-conducting material with low melting and boiling points, likely liquid or gas at room temperature. D. A brittle, opaque solid with a very high melting point. E. A non-conducting solid at room temperature that will conduct if melted or dissolved.

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

Which of the following fatty acids is best for human health? Select one: A. Fatty acids that only have single bonds between carbon atoms. B. Fatty acids that have one or more 'straight' trans-double bonds between carbon atoms. C. Fatty acids that have one or more 'bent' cis-double bonds between carbon atoms. D. All are equally bad for your health

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

Which of the following is not a compound? A. sulfur dioxide B. nitrous oxide C. water molecule D. oxygen molecule E. rust

D. oxygen molecule

What is the formula for Ethene? Select one: A. CH3 B. 2 CH2 C. C2H4 D. C2H6

C. C2H4

In the equation C22H44 + 3O22 = ? CO22 + 2H22O, how many CO22 molecules are needed to balance the equation? Select one: A. 2 B. 3 C. 4 D. 5

A. 2

Which of the following is atomic matter rather than molecular or network matter? Select one: A. Neon gas B. water C. magnesium chloride D. silver E. white gold

A. Neon gas

Which of the equations below is balanced correctly? Select one: A. Mg + N2 = MgN3 B. 2P2 + O2 = P2O5 C. CH4 +2O2 = CO2 + 2H2O D. 2Zn + O2 = ZnO E. 2C + O2 = 2CO2

C. CH4 +2O2 = CO2 + 2H2O

Why is a high temperature required for nuclear fusion to occur? Select one: A. 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. B. High temperatures magnify the strong force attraction and allow fusion to occur more readily. C. High temperatures are required to keep the fusion fuel, deuterium and tritium, stable. D. High temperatures cause the electromagnetic force to change from a repulsive force to an attractive force which helps the strong force combine the two nuclei.

A. 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 correct comparison of metals and semi-conductors? Select one: A. Metals have a larger band gap than semi-conductors. B. Metals' resistance increases when temperature increases while a semi-conductors resistance decreases. C. Semi-conductors' molecular orbitals overlap while metals' don't. D. Metals have more valence electrons than semi-conductors. E. Metals have larger electrical resistance than semi-conductors.

B. Metals' resistance increases when temperature increases while a semi-conductors resistance decreases.

What best describes how oxygen molecules would behave if mixed with water? Select one: A. They would dissolve well because they are polar. B. They would dissolve well because they are not polar. C. They would dissolve poorly or not at all because they are polar. D. They would dissolve poorly or not at all because they are not polar. E. They would dissolve well because they are ionic.

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

Which of the following processes is closest to an ideal reversible process? Select one: A. Two cars colliding. B. Using a toaster to make toast. C. A real pendulum swinging. D. A ripe peach rotting. E. An ice cube floating in a sealed insulated container of water at zero degrees.

E. An ice cube floating in a sealed insulated container of water at zero degrees.

Both fission and fusion can result in a release of energy. Why? Select one: A. The strong force is attractive over short distances and repulsive at larger distances. B. Any change to a nucleus is going to convert mass into energy. C. The nuclei of atoms with a mass of about 50 have the smallest average nucleon mass and the least energy. D. Either combining large nuclei or splitting small nuclei results in an increase in energy. This energy is released as heat.

C. The nuclei of atoms with a mass of about 50 have the smallest average nucleon mass and the least energy.

Which of the following is a true statement about melting and boiling points in materials made of covalent molecules? Select one: A. Molecules that contain double bonds melt and boil at higher temperatures because the bonds are stronger. B. Molecules that contain triple bonds are the most likely to be gases at room temperature. C. Molecules that are polar have lower melting and boiling points than non-polar molecules. D. Hydrogen bonding between molecules increases melting and boiling points. E. Van der Waals (dispersion) forces lower melting and boiling points.

D. Hydrogen bonding between molecules increases melting and boiling points.

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 the following best explains why? Select one: A. Engineers and scientists have not yet managed to make it more efficient, but there is no scientific reason it cannot be 100% efficient. B. There is too much friction in the engine and the rest of the automobile. If it were not for this friction the efficiency would be 100%. C. All engines (that is electric motors, gasoline engines, steam power generators burning gas or oil, etc.) have exactly the same efficiency, which is, of course, less than 100%. D. 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.

D. 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.

Which of the following would best describe the room temperature characteristics of the magnesium oxide? Select one: Your Response History: A. Brittle, opaque, solid. B. Electrically conducting alloy. C. Transparent gas. D. A malleable solid. E. Brittle, transparent, electrically non-conducting solid.

E. Brittle, transparent, electrically non-conducting solid.

What happens to the entropy of the universe as the products are formed? Select one: A. The total entropy stays the same. B. Thermal energy is converted into electromagnetic energy resulting in a decrease in total entropy. C. Chemical bonds are formed resulting in a decrease in total entropy. D. Chemical potential energy is converted into kinetic energy resulting in a decrease in entropy. E. Chemical potential energy is converted into thermal energy resulting in an increase in entropy.

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