PHY 100 BYU 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
In the chemical equation C6H12O6 + 3O2 ⇒ 3CO2 + 6H2O, how many oxygen atoms are on the right side of the equation?
12
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.)
2
In the equation C2H4 + 3O2 = ? CO2 + 2H2O, how many CO2 molecules are needed to balance the equation?
2
Each molecule of nitric acid has the formula HNO3. 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?
2000
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)
Two or more different elements that are chemically combined are always what kind of substance?
A compound
Which of the following is a correct comparison of metals and semi-conductors?
A metal's resistance increases when temperature increases while a semi-conductor's resistance decreases
A metal can best be described as
A network solid consisting of positively charged atoms in a sea of electrons
reactants
A starting material in a chemical reaction
Which of the following is not why alloys are useful to us today?
Alloys have a higher conductivity rate.
For the pictures of molecules, the gray balls represent carbon atoms and the white balls are hydrogen atoms. The molecules belong to a family called the hydrocarbons. These next three questions test if you can recognize patterns in molecular families and bonding around carbon atoms and then reason from them to make predictions. Ethene = Propylene = Butylene = Which of the following is a mass spectrum for propylene? (The smallest mass shown is 5.)
C (shows small red line at the 5 mass line, then some small ones between 10-20, slightly larger ones between 20-30, then very large ones around 40)
What is the formula for ethene?
C2H4
The chemical formula of the next family member after butylene will have what chemical formula?
CH2CHCH2CH2CH3 (also written C5H10)
Which of the equations below is balanced correctly?
CH4 +2O2 ⇒ CO2 + 2H2O
What happens to the entropy of the universe as the products are formed?
Chemical potential energy is converted into thermal energy resulting in an increase in entropy.
Entropy is the measure of ________ in a system.
Disorder
A very fast reaction has a very high activation energy.
False
In the future, engineers will be able to design a car that is completely efficient
False
Molecular orbitals are the same shape as atomic orbitals.
False
chemical bond rule
If the new molecular orbital is lower in an energy well and overall entropy increases, electrons go to this state and they can't get out—a chemical bond is formed. This chemical bond is stable unless energy is added.
molecular orbitals
The orbital patterns which formed standing waves for a single nucleus do not form standing waves for this new situation.
What are compounds between two different metals called?
alloys
Which of the following processes is closest to an ideal reversible process?
an ice cube in a glass of water at zero degrees
Which of the following is not a characteristic of a metal or alloy?
brittle
Which of the following would best describe the room-temperature characteristics of an ionic substance?
brittle, transparent, electrically non-conducting solid
mass spectrometer
•Molecules are introduced into the mass spectrometer. •Molecules are ionized, breaking most of them into molecular fragments and individual atoms. •A force is applied. This force is the same on all of the fragments so, according to Newton's 2nd law, the fragments with the smallest mass will have the largest acceleration. •The fragments arrive at the detection screen. They arrive in groups, with the least massive fragments arriving first. •The number of fragments of each mass is recorded on a screen.
Rank the following according to their strength, weakest first, strongest last.
dispersion forces, dipole-dipole interactions, hydrogen bonding, covalent bonding
intermolecular forces
electromagnetic forces between individual molecules. These forces are weak when compared to the forces between the individual atoms making up the molecule itself.
surroundings
everything outside the system
Dispersion forces are stronger than covalent bonds.
false
Light can only be seen through very thin metal.
false
The energies of the orbitals that form when metals interact are very widely spaced in energy.
false
The forces between the N2 molecules are very strong.
false
metals have higher ionization energies than nonmetals do
false
Complete conversion of one form of energy to another can occur only in which direction?
from higher to lower organized forms
Which of the following set of properties is most likely those associated with methane, a covalently bonded compound?
gas at room temperature, colorless, does not conduct electricity when solid
These graphs show energy as a function of time for several different reactions. Which of the reactions shown below would end up absorbing energy from the surroundings?
graph goes up slightly but never returns all the way down to where the energy line is
Which type of energy is the most ordered?
gravitational potential energy
polar molecule
if the dipoles of the individual parts of the molecule add up to create a total dipole for the entire molecule
In a bonding orbital between two atoms, where is the electron density the highest? (Where do you have the highest probability of detecting an electron?)
in between the two atoms
atomic matter
individual atoms with little or no interaction between the individual atoms themselves
hydrogen bonds
interactions between hydrogen atoms bound to oxygen, nitrogen, or fluorine atoms or fluorine atoms bound with oxygen, nitrogen, or other fluorine atoms. Hydrogen bonds are among the strongest of the intermolecular interactions.
An ice cube melts in a glass of warm water. This is an example of which type of process?
irreversible
solutions
liquid mixtures of compounds- one or more compounds are dissolved in another type of compound, such as water
Which of the following is atomic matter rather than molecular or network matter?
neon gas
Which of the following tends to have the highest melting and boiling points?
network matter
salts
non-metals and metals together also form network matter
Ionic compounds are formed between a metal and a
nonmetal
Buckminsterfullerenes
one of the ways carbon satisfies the octet rule. Has a free electron and can conduct electricity.
The various forms of energy can be ranked according to their level of what?
organization
Elements
pure substances composed of one kind of atom only. basically, your elements of the period table.
Compounds
pure substances composed of two or more kinds of atoms. Examples of compounds include lactose, casein, water, and carbon dioxide.
activation entropy
reactions will only take place when the reactants are lined up in a particular orientation.
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
Which is the best definition of an alloy?
solid mixture of metals
Blends or composites
solid mixtures of compounds
Alloys
solid mixtures of different metals
law of increasing disorder/the 2nd law of thermodynamics
states that the total amount of disorder in the universe either remains the same, for a reversible process, or increased, for an irreversible process
products
the end result of a chemical reaction
Which of the following is the best description of activation energy?
the energy that must be put into a system before a reaction can take place.
network matter
the individual atoms interact strongly with many of their neighbors
chemical bonds
the interactions between the atoms in a single molecule or network matter. There are three main types of bonds: metallic, ionic, and covalent
The oxidation state of an atom refers to
the number of electrons gained or lost when an ionic bond is formed.
systems
the part of the world we want to isolate and study
universe
the system and the surroundings put together
Metals have a greater tendency than nonmetals to lose electrons.
true
N2 has a triple bond and is a gas at room temperature. The triple bond is a very strong bond.
true
Vibrational Spectroscopy
used to study molecules and their bonds. In vibrational spectroscopy, the amount of electromagnetic radiation absorbed by a molecule is measured as the frequency of the electromagnetic radiation is varied.
dispersion forces
weak intermolecular attractions between nonpolar molecules arising from the formation of temporary dipoles.
dipole-dipole interactions
weak intermolecular attractions between polar molecules
octet rule
when an ion forms, it is most energetically favorable to get to a noble gas configuration of ns2np6
single bond
when atoms share a pair of electrons
triple bond
when atoms share three pairs of electrons
double bond
when atoms share two pairs of electrons
If a certain LED (doped semi-conductor) is cooled in liquid nitrogen, the color moves to a higher frequency. What happens to the band gap?
It increases in energy
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 is an ionic compound?
MgF2
Which of the following pairs would you expect to be covalently bonded?
S and Br
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?
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.
bonding orbital
The first molecular orbital, a chemical bond can occur with this type of orbital and the electrons have a high probability of being between the two atoms
What happens to the valence electrons as the product (MgO) is formed?
The magnesium atoms' valence electrons are effectively transferred to oxygen.
What happens to the valence electrons as an ionic compound is formed?
The metal atoms' valence electrons are effectively transferred to the nonmetal.
An air conditioner causes a cool place (the inside of your house) to become colder, but at the same time heats up a warmer space. (An air conditioner blows hot air out the back, heating up the outside air even more). 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.
anti-bonding orbital
The second type of orbital is called this because there is a low probability of electrons being between the two atoms
dipole
The separation of positive and negative charges due to the polar bond, is stronger if the charges are separated more.
A reversible process does what to the total disorder in the universe?
The total disorder does not change
Energy and entropy are both involved in chemical reactions.
True
polar covalent bond
When a bond forms between two (or more) atoms with different electronegativities, the electrons will spend more time near the atoms with high electronegativities and less time near the atoms with lower electronegativities.
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
molecular ion
a group of atoms covalently bound to each other that have a net charge because electrons have been lost or gained in order to form a stable covalent molecule
electronegativity
a measure of how strongly atoms attract electrons. Electronegativity increases from the left to right across the rows of the periodic table and decreases down a column of the periodic table.
Pure Substances
chemical matter that has a defined and unchanging chemical composition
Which of the following is not used as a measurement technique for identifying chemical substances?
color spectroscopy
Mixtures
contain multiple substances. With effort, a little or lot, depending upon the mixture, the mixture can be separated out into groups of pure substances.
Which of the following substances is most likely to be a pure element?
copper
