Chem Exam pt 1
The half-life of carbon-14 is 5730 years. A sample is found to have one-eighth the original amount of carbon-14 in it. How old is the sample?*
17,200 years
If the concentration of gold in seawater is 2.0 milligram per ton of sea water and the mass of the ocean is 1.5 × 10 18 tons, how much gold is in the ocean?
3.0x10^12kg
The following statement describes which subatomic particle best? It has a relatively large mass.
A proton and a neutron
How is the term photon related to the term quantum?
A quantum of light is actually one photon.
Which of the following statements about strong and weak acids is not true?
A weak acid is as corrosive as a strong acid.
A beam of protons and a beam of neutrons of the same energy are both harmful to living tissue. The beam of neutrons, however, is less harmful. Why?
Neutrons carry no electric charge and thus have a greater likelihood of passing through the tissue.
Why might the following nuclear reaction not be very good for energy production in a fission reactor?Fe → Si + Mg + 3 neutrons*
The reactants are too small to obtain energy from the missing mass due to strong nuclear force.
Oxygen, O 2, is certainly good for you. Does it follow that if small amounts of oxygen are good for you then large amounts of oxygen would be especially good for you?
No. Breathing 100% oxygen for extended periods of time can be damaging to the body.
Why can't we see atoms?
We see with light energy and the wavelength is larger than the object and so it is not reflected.
Red blood cells have a high concentration of dissolved ions. When placed into pure water they rupture. Why?
Osmosis draws water into the cell until it pops.
What does Einstein's energy equation (E = mc 2) say about the energy that is derived from nuclear fission reactions?*
The energy released is due to the missing mass of the products compared to the mass of the starting materials.
Which of the following statements best describes the strong nuclear force?
The force is very strong but has a very short range.
Why might sodium carbonate (washing soda, Na 2CO 3) be added to hard water to aid in cleaning?
The hard ions in the water are more attracted to the carbonate ions -2 charge.
Describe what usually happens to a hot solution that is saturated with a solid as it cools.
Some of the solid comes out of the solution
Half-frozen fruit punch is always sweeter than the same fruit punch completely melted because
crystallization is a purifying process
Which of the following diagrams best represents the size of the atomic nucleus relative to the size of the atom?
d
The ________ represents the complete range of frequencies of light energy from radio waves to cosmic rays.
electromagnetic spectrum
When blue food coloring is stirred into water, the result is a*
homogeneous mixture called a solution.
The following image describes which type of change?
physical change
According to the shell model, how many shells are required to describe the periodic table?
seven
Suppose that a certain atom possesses only four distinct energy levels. Assuming that all transitions between levels are possible, how many spectral lines will this atom exhibit?
six
Some products on the market today involving nanotechnology include
sunscreen. elevators. cosmetics. cars.
Which chemical family is composed almost entirely of man-made elements?
the actinides
What is activation energy?
the minimum amount of energy to break the bonds in reactants
Mixtures can be separated into their components by taking advantage of differences in the chemical properties of the components. Why might this separation method be less convenient than taking advantage of differences in the physical properties of the components?*
A chemical property involves a chemical change so that you no longer have what you had.
Why is it better to recycle metals than to mine more?
It takes far less energy to recycle
Why is recycling of aluminum better for the environment than electrolysis of bauxite (an aluminum ore)?
It takes less energy to recycle aluminum.
List the following bonds in order of increasing polarity.
N-N < N-O < N-F < H-F
What is a rem?
a unit for measuring radiation exposure
If a neutral atom gains two electrons, what is the electrical charge of the atom?
-2
Which of the following solutions is the most concentrated?
0.5 L of a 3 molar solution
There are about
100 different types of atoms
How many atoms of Oxygen (O) are in H^3OClO 4?
5
How many atoms are in one molecule of Na ^2SO 4?
7
How many alpha particles are emitted in the series of radioactive decay events from a U-238 nucleus to a Pb-206 nucleus?*
8
An atom absorbs or emits only particular frequencies of light. White light bends into a glass prism and separates into a rainbow of colors. In which of these two scenarios does the electromagnetic radiation behave as a wave? As a particle?
Absorption of light shows particle behavior while bending of light shows wave behavior.
What is the easiest way to eliminate organic components?
Aerate the solution and let bacteria consume the organics.
Is aging primarily an example of a physical or chemical change?
Aging is an example of a chemical change involving the chemical reformation of our biomolecules.
Is chemistry the study of the submicroscopic, the microscopic, or the macroscopic, or all three?
All of the above because most everything is made of atoms and molecules.
Which of the following elements is a gas at room temperature?
Argon (ar)
Which of the following statements about electrons is true?
Electrons behave like waves. Electrons have a negative charge. Electrons are particles. Electrons in atoms can be excited by light energy.
Which of the following is most likely to have the weakest induced dipole-induced dipole interaction?*
F2
Hydrogen chloride, HCl, is a gas at room temperature. Would you expect this material to be very soluble or not very soluble in water?
HCl is very soluble in water by virtue of the dipole/dipole attractions occurring between the HCl and H 2O molecules.
Bond energies increase in going from C-N (lowest) to C-O to C-F (highest). Explain this trend based upon the atomic sizes of these atoms as deduced from their positions in the periodic table.
In going from nitrogen to oxygen to fluorine the atoms get smaller. This means that the bonding atoms are closer together, which translates into a greater bond energy.
Why isn't dirt listen in the periodic table?
The periodic table lists only elements made of one kind of material. Dirt is a mixture of elements and compounds.
Why might the following nuclear reaction not be very good for energy production in a fission reactor?*
The products are not the right size to obtain much energy from missing mass due to strong nuclear force.
Why is the combination of two protons and two neutrons stable, but two protons and one neutron is not?
There are not enough neutrons to overcome the electrical repulsion of the protons.
Which are older, the atoms in the body of an elderly person or those in the body of a baby?
They are of the same age, which is appreciably older than the solar system.
Atoms of metallic elements can form ionic bonds, but they are not very good at forming covalent bonds. Why?
They have a great tendency to lose electrons.
Wild plants readily grow "all by themselves" yet the molecules of the growing plant have less entropy than the materials used to make the plant. How is it possible for a there to be this decrease in entropy for a process that occurs all by itself?
Wild plants don't grow "all by themselves." When we consider the entire system, including the sun, we find an overall increase in entropy.
Fatty acid molecules can also align to form a bilipid layer that extends in 3-dimensions. Shown below is a cross section of this structure. What is this structure called? (Hint: it forms the basis of all life.)
a cell
Which of the following best describes a conceptual model of an atom?
a model that illustrates the tendency of an atom to undergo chemical bonding
Which of the following images could describe an element at the atomic level?
all
When 226/88 Ra decays by emitting an alpha particle, what is the atomic number of the resulting nucleus? What is the resulting atomic mass?
atomic number = 86; atomic mass = 222
The image below shows a beam of radiation passing between two electrically charged plates. Which of the beams is due to an energetic light wave?
b
Which of the following boxes represents a compound?
c
A neutron makes a better nuclear bullet than a proton or an electron because it*
carries no electrical charge
People who work around radioactivity wear film badges to monitor the amount of radiation that reaches their bodies. These badges consist of small pieces of photographic film enclosed in a light-proof wrapper. What kind of radiation do these devices monitor?
gamma radiation
Which of these does not describe a metal at room temperature?
gas
Which of the following is not a typical use for potable water?
irrigation
The neon atom tends not to lose any electrons because
of its relatively strong effective nuclear charge.
The portion of the atmosphere that filters out 95 percent of the incident UV radiation is the
ozone layer
Dipole-induced dipole forces of attraction exist between water and gasoline, and yet these two substances do not mix because water has such a strong attraction for itself. Which of the following compounds might best help to make these two substances mix into a single liquid phase?
the molecule on the far left because the O-H bond is polar and the carbon and hydrogen bonds are nonpolar
Which of the following molecules is polar?
the one with two h's one left and two fs on right
Oxygen, O, (number 8), sulfur, S, (number 16), and selenium, Se, (number 34) have such similar chemical properties because
their outermost shells contain the same number of electrons.