1.
The spectroscopic (electron) configuration of an atom is [He]2s22p4. Which element is this?
Correct Answer
E. ₈O
Explanation
If the answer is not known offhand, it may be deduced if all the information present is used. First, an atom is specified in the question, meaning it is uncharged; therefore, the number of electrons will equal the number of protons. Second, the superscripts in 2s²2p⁴ show six electrons. Looking at the answers, helium (He) is listed as having two protons, and thus must have two electrons. Adding six electrons (for 2s²2p⁴) and two electrons (for helium) gives a total of eight electrons for the unknown atom. This means it must have eight protons if it is not an ion. A glance at the answers shows oxygen has eight protons and fits the bill.
2.
Which of the following elements is NOT a gas at room temperature (20°C)?
Correct Answer
B. Bromine
Explanation
Bromine is a liquid at room temperature. Oxygen and nitrogen exist as molecules of diatomic gases. Argon and krypton are monatomic gases at 20°C.
3.
All things being equal, the deBroglie wavelength is greater for a particle of
Correct Answer
A. Higher speed
Explanation
The deBroglie wavelength is inversely proportional to the particles speed
4.
A particle and its antiparticle have
Correct Answer
D. A and C
Explanation
Particles and antiparticles have opposite charges and the same mass. The momenta for both will be the same since the masses are the same.
5.
When a nucleus undergoes beta decay, which of the following remains constant?
Correct Answer
A. The atomic-mass number
Explanation
The number of nucleons remains unchanged in beta decay, so the mass number remains the same. The atomic number changes by one unit. The change in nuclear spin is not determined by the reaction.
6.
Heavy nuclei release energy during fission because
Correct Answer
C. The binding energy per nucleon is greater for medium-mass nuclei.
Explanation
Energy released during fission comes from the change of nuclear binding energy. The electrons do not play a role in the reaction, so choices A. and B. are wrong. Neutrons are not transformed to electrons or gamma rays, which eliminates choices D. and E.
7.
When a nucleus undergoes alpha decay
Correct Answer
D. A and B
Explanation
Alpha decay is the emission of a helium-4 nucleus, which consists of two protons and two neutrons. The atomic number changes because two protons are emitted; the mass number changes because four nucleons are emitted.
8.
Radioactive decay of a nucleus
Vertical axis: number of nuclei remaining
Horizontal axis: time
Select the graph below that best illustrates this.
Correct Answer
A. A
Explanation
Radioactive decay is an exponential decrease in the number of nuclei. Graphs C. and E. do not quite follow exponential decay.
9.
A mass experiencing a constant acceleration
Vertical axis: distance
Horizontal axis: time
Select the graph below that best illustrates this.
Correct Answer
B. B
Explanation
Distance traveled is proportional to the square of the time.
10.
A solid is slowly heated past its melting point
Vertical axis: temperature
Horizontal axis: time
Select the graph below that best illustrates this.
Correct Answer
D. D
Explanation
The temperature increases until the melting point is reached. It remains constant until the solid melts, then continues to increase.
11.
Static magnetic fields are caused by
Correct Answer
B. Electric charges in motion.
Explanation
Magnetostatic fields are caused by constant electrical currents: electric charges in motion. There are no magnetic charges, so choices C. and D. are incorrect. Static electric charges produce only electrostatic fields, so choice A. is incorrect.
12.
Isotopes of an element have the same number of _______ but different numbers of _______.
Correct Answer
B. Protons, neutrons
Explanation
While it might appear that choice D. is also correct it would be so only for atoms, but not ions, of an element.
13.
Which of the following pairs is most useful in determining a rock's origin?
Correct Answer
D. Composition and texture
Explanation
The origin of a rock is most clearly seen through its composition and texture. These two in combination, more than any of the other pairs, tell what the rock is made of and how it came to be that way.
14.
Which of the following is an example of a one-way change?
Correct Answer
E. The evolution of animal life
Explanation
The evolution of animal life, choice E., is the only choice that is an example of a one-way change. There is no theory or evidence of a reversal or a cycle to evolution. All the other examples run in cycles.
15.
What materials are trapped in the Van Allen belts of the earth's magnetic field?
Correct Answer
A. Atomic particles
Explanation
Since the Van Allen radiation belts are magnetic in nature, the only particles they would trap would have to be very small and charged. Atomic particles are the only one of the choices that would be small enough and have the possibility of being charged.
16.
Static magnetic fields exert forces on
Correct Answer
B. Electric charges in motion.
Explanation
Magnetic fields act only on moving electric charges. Choices A. and C. refer to static phenomena, which magnetic fields do not affect. Magnetic charges do not exist.
17.
Light and sound share which of the following qualities?
Correct Answer
D. Both exhibit diffraction and interference.
Explanation
Light and sound are both waves, so they both exhibit diffraction and interference. Only light is transverse and electromagnetic; only sound requires a medium for propagation.
18.
A rocket is traveling near the speed of light with respect to an observer. Compared to this observer's clocks, a clock on the rocket appears to run
Correct Answer
A. More slowly.
Explanation
According to special relativity, moving clocks experience time dilation, which means that they appear slow to stationary observers. The direction of motion is irrelevant, as is the type or construction of the clock.
19.
A book rests on a level table. The force holding it up is
Correct Answer
C. Electromagnetic
Explanation
Electrostatic repulsion of electrons between the atoms of the book and the atoms of the table prevent the book from penetrating the table. Nuclear forces do not play a role. Gravitation pulls the book down, toward the table. Friction, while it is an electromagnetic force, is not required hold up the book.
20.
It is often said that matter consists mostly of empty space. This statement is
Correct Answer
C. True because atomic nuclei and electrons have a small volume compared to that of an atom.
Explanation
Electrons are point-like particles and the nucleus has a radius much smaller than an atom.
21.
According to the special theory of relativity, observers in all inertial frames agree on the measurement of
Correct Answer
D. A and B
Explanation
Rest mass and charge are invariants, i.e., the same in all inertial frames.
22.
An airplane is traveling horizontally at a constant velocity of 100m/s at a height of 122m. The pilot wants to drop a package into a net on the ground. When should he release it? (Note: neglect friction.)
Correct Answer
B. 500m before the net
Explanation
The vertical and horizontal motions are independent. First, use height = (1/2)gt2 to find the time required for the package to fall to the ground: t = 5s. Then, multiply by the speed of the airplane to find the horizontal distance the package will travel before hitting the ground: 100 ∙ 5 = 500m.
23.
When an unbalanced force acts on an object in motion
Correct Answer
E. A, B, and C
Explanation
Newton's second law says that acceleration is proportional to net force. This means that there must be a change of velocity. The speed can increase or decrease. It can remain the same if the direction of the velocity changes, as in uniform circular motion.
24.
Diffraction of waves passing through a circular aperture depends on the
Correct Answer
D. Ratio of the wavelength to the diameter.
Explanation
Only the ratio of the wavelength to the diameter is required to find angles of diffraction. Amplitude does not affect the diffraction of waves.
25.
The correct formula for calcium chloride is:
Correct Answer
D. CaCl₂
Explanation
Calcium's symbol is Ca, and chlorine's symbol is Cl. Calcium is an alkaline earth metal (2, 2A, or IIA), which means it forms a +2 ion. Chlorine is a halogen (17, 7B, or VIIA) and forms a -1 ion. The compound would be ionic (formed from elements on opposite sides of the periodic table): Ca+2Cl-1. Writing the superscript of one ion as the subscript of the other gives the correct formula: l2, or more properly, CaCl2. Choice A. implies three elements: calcium, carbon, and an unknown element known as L.
26.
Given that the oxidation state of oxygen is –2 (–II), and of hydrogen +1 (+I), what is the oxidation number (state) of sulfur in sulfuric acid, H2SO4?
Correct Answer
E. +6
Explanation
The oxidation number (state) of sulfur is +6 (+VI). This is calculated as:
oxidation number for H is +1 × 2 hydrogen atoms = +2
oxidation number for O is –2 × 4 oxygen atoms = –8
The oxidation number for H and O together is = –6.
Therefore, sulfur must have an oxidation number of +6 if the algebraic sum of all the oxidation states is to equal zero.
27.
The following reaction occurs when iron is pickled. Choose the answer that correctly shows the balanced equation.
HCl + Fe2O3 → FeCl3 + H2O
Correct Answer
D. 6HCl + Fe₂O₃ → 2FeCl₃ + 3H₂O
Explanation
Use the subscripts of the compounds on one side of the equation to suggest coefficients for compounds on the other side. The subscript 3 in FeCl3 suggests that a coefficient of 3 should be tried before the reactant that also contains chloride, yielding: (1) 3HCl + Fe2O3 → FeCl3 + H2O
In the same manner, the subscript 2 in Fe2O3suggests putting a coefficient of 2 in front of FeCl3, or:
(2) 3HCl + Fe2O3 → 2FeCl3+ H2O
Finally, the presence of 6 chloride ions in 2FeCl3indicates 6 chloride ions are needed in the reactant, as in: 6HCl.
28.
Given that the oxidation state of oxygen is –2 (–II), and of hydrogen +1 (+I), what is the oxidation number (state) of sulfur in sulfuric acid, H2SO4?
Correct Answer
E. +6
Explanation
The oxidation number (state) of sulfur is +6 (+VI). This is calculated as:
oxidation number for H is +1 × 2 hydrogen atoms = +2
oxidation number for O is –2 × 4 oxygen atoms = –8
The oxidation number for H and O together is = –6.
Therefore, sulfur must have an oxidation number of +6 if the algebraic sum of all the oxidation states is to equal zero.
29.
The following reaction occurs when iron is pickled. Choose the answer that correctly shows the balanced equation.
HCl + Fe2O3 → FeCl3 + H2O
Correct Answer
D. 6HCl + Fe₂O₃ → 2FeCl₃ + 3H₂O
Explanation
Use the subscripts of the compounds on one side of the equation to suggest coefficients for compounds on the other side. The subscript 3 in FeCl₃ suggests that a coefficient of 3 should be tried before the reactant that also contains chloride, yielding: (1) 3HCl + Fe₂O₃ → FeCl₃ + H₂O
In the same manner, the subscript 2 in Fe₂O₃ suggests putting a coefficient of 2 in front of FeCl₃, or:
(2) 3HCl + Fe₂O₃ → 2FeCl₃+ H₂O
Finally, the presence of 6 chloride ions in 2FeCl3indicates 6 chloride ions are needed in the reactant, as in: 6HCl.
30.
What percentage, by volume, of the earth's crust is made up of oxygen?
Correct Answer
D. More than 90 percent
Explanation
A simple analysis of the earth's crust shows it to be by volume more than 90 percent oxygen.
31.
What is the average density of the earth?
Correct Answer
C. 5.5 gm/cm³
Explanation
The average density of the earth is close to the most abundant element, which is iron. The density of iron is closest to choice C.
32.
What is the approximate radius of the earth in km?
Correct Answer
E. 6,400
Explanation
The radius of the earth is approximately 6,400 km. Choice B. is the circumference in miles, and choice D. is the diameter in miles.
33.
When light enters a transparent medium from the vacuum the
Correct Answer
D. Wavelength decreases
Explanation
The wavelength in a medium is inversely proportional to the refractive index, which is unity for vacuum, and greater than one for all materials. The frequency is not affected. The speed of propagation is inversely proportional to refractive index, so it decreases also.
34.
As the temperature of a blackbody increases, the emission of radiation
Correct Answer
C. Increases at all wavelengths
Explanation
While the peak emission shifts to shorter wavelengths as the temperature of a blackbody increases, the emission increases at all wavelengths.
35.
For a mass in uniform circular motion, the following remains constant:
Correct Answer
D. Kinetic energy
Explanation
The speed is constant in uniform circular motion, so the kinetic energy remains constant. Velocity, force, acceleration, and momentum are all vectors. While their magnitudes remain constant, their directions do not.
36.
When a charged particle moves in a constant magnetic field its
Correct Answer
B. Speed remains the same.
Explanation
The magnetic force acts perpendicular to the velocity, so it does no work on the particle. Consequently, the speed remains constant.
37.
The internal energy of a monatomic ideal gas depends on the temperature
Correct Answer
C. And the number of moles
Explanation
The temperature determines the kinetic energy per atom or molecule of the gas. The total internal energy also depends on the number of molecules.
38.
When a monatomic ideal gas is heated in a closed, rigid container
Correct Answer
A. The entropy increases
Explanation
When heat is added to a substance, the entropy increases. Choice B. is incorrect because the gas can do no work at constant volume. Choice C. is incorrect because the specific heat of an ideal gas is independent of temperature.
39.
A small child, traveling in a car, throws a toy horizontally out the window at 0.5m/s from a height of 1.22m. At the same instant, she drops her bottle from the same height. Which of the following is true if friction is neglected?
Correct Answer
C. The bottle and the toy hit the ground at the same time.
Explanation
Vertical and horizontal motion are independent. Both objects take the same amount of time to fall.
40.
A rocket is traveling along the x-axis past an observer at high speed. Two simultaneous events in the rocket are
Correct Answer
D. Simultaneous to the observer if they both occur at the same x-coordinate.
Explanation
In general, events that are simultaneous in one reference frame are not in another. However, if the events are only separated from each other in a direction perpendicular to the relative motion, they are simultaneous in both frames. Choice C. is incorrect because the x-axis is the direction of motion. Choice E. is incorrect because the two events need not be co-located to be simultaneous in two frames.
41.
Two masses collide and stick together. In this collision,
Correct Answer
D. B and C
Explanation
Only linear and angular momentum are conserved in inelastic collisions.
42.
Which of following statements about water is INCORRECT?
Correct Answer
E. Hydrogen bonding causes water to increase in density down to the point of freezing (0˚C).
Explanation
Water has a maximum density at 40˚C. Below that temperature in the liquid phase and as ice, water molecules are spaced farther apart than in water above 40˚ C. This makes ice—solid water—less dense than liquid water, and as a result, ice floats rather than sinks in water.
43.
Which chemical name is correctly paired with its proper formula?
Correct Answer
D. Iron (III) chloride: FeCl₃
Explanation
LiOH is a hydroxide, and ZnSO4 is zinc sulfate, while ammonium hydroxide cannot be NH4Cl (but ammonium hydroxide can be, and is). Sulfur hexafluoride is SF6 and not SF5 (sulfur pentafluoride). Since each chloride has a -1 charge, assigning a +3 value to iron—iron (III) ion—is correct.
44.
A compound is determined to have the empirical formula CH2O and a molecular weight of 180. What is the correct molecular formula for this compound? (Oxygen has an atomic weight of 16, carbon is 12, and hydrogen is 1.
Correct Answer
E. C₆H₁₂O₆
Explanation
The molecular weight (mw) for CH₂O is 30, while the molecular weight for the actual compound is 180. To determine the correct molecule formula, try increasing the number of atoms in each molecule while retaining the same ratio of atoms, and check the resulting molecular weights. That is, multiply by two to give C₂H₄O₂ (mw of 60), by three to give C₃H6O₃ (mw of 90), and so on, until the correct molecular weight (and therefore the correct molecular formula) is reached.
45.
Warm air tends to rise through cooler air because
Correct Answer
B. It is less dense.
Explanation
When air is heated, like most things, it expands. Having more volume, with the same mass, makes it less dense, or choice B.
46.
What gas is most effective in reducing heat loss from the earth by absorbing re-radiated heat energy?
Correct Answer
D. Carbon dioxide
Explanation
When solar energy bounces off the earth, it loses some of its strength. The high-energy, short-wavelength, solar rays turn into low-energy, long-wavelength radiation. The nature of carbon dioxide is that it will readily absorb the energy from these long waves.
47.
Which of the following mineral characteristics is NOT determined by the way the atoms are arranged?
Correct Answer
B. Color
Explanation
The only characteristic of a rock that has nothing to do with the way the atoms are arranged is color. Color involves the electrons and their energy levels, not the arrangements of entire atoms.
48.
If a planet is in orbit 4 AU from the sun, how long will it take to orbit the sun?
Correct Answer
B. Eight years
Explanation
You can find this by using Kepler's third law, which states that the square of the period of revolution in years is proportional to the cube of the average distance between the sun and planet in Astronomical Units.
49.
Star A has an apparent magnitude of –2, and Star B has an apparent magnitude of +3. Which of the following statements is true?
Correct Answer
E. None of the above
Explanation
The smaller the number, the brighter the star. Each magnitude means a star appears 2.51 times brighter or dimmer, so Star A is 100 times brighter than Star B.
50.
Compared with Population II stars, Population I stars
Correct Answer
A. Are younger.
Explanation
Population I stars, like the sun, are relatively young and have a greater abundance of heavy elements than Population II stars have.