PHYS 100 Chapter 18 - 25
What is the formula for Ethene?
C2H4
Which of the equations below is balanced correctly?
CH4 +2O2 = CO2 + 2H2O
What would be the chemical formula of the ionic compound between calcium and bromine?
CaBr2
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.
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.
How does a catalyst affect a reaction?
It lowers the activation energy
Magnesium chloride forms a solid in which two chloride ions are found for every magnesium ion but no discrete molecules are observed in the solid. What is the simplest formula for this compound?
MgCl2
Consider a refrigerator and its contents to be the system. Warm food is cooled to a lower temperature. Warm water is cooled in the freezer and eventually frozen to ice. Do these two processes, cooling food and freezing water, increase the entropy inside the refrigerator?
No
If you were to put your hand behind the back of an operating refrigerator, would you feel cold air coming out of the exhaust?
No
Can sulfur be considered a compound and why?
No, it is composed of only one type of atom
What is the chemical formula for sulfur?
S8
What are the electrons in a covalent bond doing?
Shared between specific pairs of atoms
In carbon tetra-chloride, CCl4, what is true about the charge distribution?
The chlorine will be more negative than the carbon.
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 melting temperature as the size of the molecule increases?
The melting temperature increases with size.
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.
What best describes how oxygen molecules would behave if mixed with water?
They would dissolve poorly or not at all because they are not polar.
Fish that swim in the cold north Atlantic would have what type of fatty acid in their blood?
Unsaturated acids with lots of double
When do polyatomic ions form crystals?
When they combine with metal atoms to form salts and When they combine with other non-metal atoms.
When are molecules conductors of electricity?
When they combine with metals and are then melted or dissolved
Uranium-238 alpha decays, emitting a helium-4 nucleus. What is the mass number of the product?
234
Which of the following is a correct and balanced equation showing the reaction of calcium and oxygen?
2Ca + O2 = 2CaO
If one oxygen and one carbon atom combine to make CO, how many total electrons need to be shared to complete both atom's valence shells? (Add the number C needs to the number O needs.)
6
If GaAs forms a semiconductor like Ge, which of the following elements will form a semiconductor like Si?
Al and P
Figure 1 shows that gas molecules are present inside the box. Figure 2 shows that there is a vacuum (no gas molecules present) inside of the box. If the two figures represent snapshots in time of an irreversible process, which figure came first and why?
Because an empty box is more ordered.
The force that holds atoms together to make molecules
covalent bond
Which of the following is NOT why alloys are useful to us today? Alloys
have a higher conductivity rate.
How would you describe the melting point of a substance formed by a substance containing molecular ions?
high
What happens to the number of MO's as the number of atoms that come together increases?
increases
In an irreversible process, the overall disorder of the universe
increases.
What determines melting point?
length of molecule, number of double bonds, type of double bond, location of double bond, shape of molecule
Which type of atom has valence electrons higher in the energy well?
metal
Which of the following is atomic matter rather than molecular or network matter?
neon gas
What classification of matter is magnesium chloride?
network matter
Which type of atom has the highest ionization energy?
non-metal
How many double bonds exist between carbon atoms in these unsaturated fatty acids?
one or more
Which of the following is not a compound?
oxygen molecule
If two chlorine atoms combine to make Cl2, what type of bond will exist between them?
single
What happens to the energy of the Mg and Cl atoms as this compound is formed?
the energy decreases
What happens to the overall entropy in the universe as this compound is formed?
the entropy increases
If one oxygen and one carbon atom combine to make CO, what type of bond will exist between them?
triple
How many double bonds exist between carbon atoms in these saturated fatty acids?
zero
Which of the following processes is closest to an ideal reversible process?
An ice cube floating in a glass of water at zero degrees.
When you compare saturated with unsaturated fatty acids containing the same number of carbon atoms, what is true?
Saturated fatty acids have more hydrogen
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.
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:
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.
If two chlorine atoms combine to make Cl2, how many electrons does each of the chlorine atoms need to complete its valence shell?
q
Which type of energy listed below is the most ordered?
Gravitational potential energy
Which of the following tends to have the highest melting and boiling points?
network matter
Predict how many electrons Mg would be expected to lose in ionic compounds.
2
How many nonmetals atoms (bromine) are needed to take all of the electrons that the metal atoms (calcium) want to give?
2 Bromine atoms, 1 Calcium atom
Which of the images below has a molecular structure where the silicate ions are connected to each other without any metal atoms sandwiched between them?
*crystals picture*
Which of the fatty acids pictured below contains a trans bond?
*straigght line with one double bond in the middle*
What would be the charge of calcium, Ca, in order to satisfy the octet rule? Hint: look at the column number.
+2
What is the charge of iron (Fe) in the compound Fe2O3?
+3
What would be the charge of bromine, Br, in order to satisfy the octet rule? Hint: look at the column number.
-1
How many electrons does Cl want to gain?
1
How many electrons would potassium, K, need to get rid of to satisfy the octet rule?
1
The 2nd 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.
Which of the following would best describe the characteristics of covalent materials?
A non-conducting material with low melting and boiling points, likely liquid or gas at room temperature.
In order for a chemical reaction to occur:
Entropy must increase as a result of the reaction.
A car can't convert all of the energy from its fuel to macroscopic kinetic energy. Why?
Entropy would decrease.
What types of atoms make covalent bonds?
all non-metals
Why are metals opaque?
because metals have empty, overlapping orbitals for their electrons
gas + gas --> gas + vapor
both energy and entropy change
solid + gas --> gas + vapor
both energy and entropy change
Does a double bond between two carbon atoms increase or decrease the number of hydrogen atoms that could bond to carbon in these molecules?
decrease
Would a double bond between two carbon atoms increase or decrease the number of hydrogen atoms that could bond to carbon in these molecules?
decrease
What happens to the spacing between the energy of one MO and the next one immediately above or below it as the number of atoms that come together increases?
decreases
The force that holds molecules that have positive and negative sides to one another
dipole interaction
The force that holds molecules that do not have positive and negative sides to one another
dispersion force
If two oxygen atoms combine to make O2, what type of bond will exist between them?
double
gas + gas --> vapor
energy is given off
Because it is possible to separate the atoms back into different areas, the process is reversible.
false
Current can flow in all directions in an LED.
false
In which of the following processes is the end product more ordered than the reactants?
gas + gas = gas
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?
2000
If two nitrogen atoms combine to make N2, how many electrons does each of the nitrogen atoms need to complete its valence shell?
3
Each molecule of methane has the formula 𝐶𝐻4. If there are 4000 carbon atoms present how many hydrogen atoms will be required to convert all of the carbon atoms into methane?
16000
How many electrons would sulfur need to gain to satisfy the octet rule?
2
If two oxygen atoms combine to make O2, how many electrons does each of the oxygen atoms need to complete its valence shell?
2
In the equation C2H4 + 3O2 = ? CO2 + 2H2O, how many CO2 molecules are needed to balance the equation?
2
Now ask yourself how many metal atoms (potassium) are needed to give all of the electrons that the nonmetal atoms (sulfur) want to take?
2
Which of the following would best describe the room temperature characteristics of the magnesium oxide?
Brittle, transparent, electrically non-conducting solid.
Metals have higher ionization energies than non-metals do.
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.
We see a large amount of order in the world around us from life to currents in the air and ocean. How is this consistent with the Law of Increasing Disorder?
It is because the sun provides additional high-order energy to the world to create this order.
Which of the following is a correct comparison of metals and semi-conductors?
Metals' resistance increases when temperature increases while a semi-conductors resistance decreases.
Ammonium nitrate (NH4NO3), a common fertilizer, is an ionically bonded substance involving two polyatomic ions, ammonium (NH4+) and nitrate (NO3−). Ammonium nitrate dissolves well in a polar solvent such as water. Which of the following statements best describes what happens when this fertilizer dissolves in water?
The compound breaks up into the two oppositely charged ions. The ions do not break apart.
Instead of cold air coming from the operation of the exhaust of the refirgerator, you would feel hot air. The hot air increases the temperature of the surroundings. Is this a process that increases the entropy of the kitchen?
Yes. Since hot air causes disorder, increasing the temperature would increase the entropy of the room.
If the entropy associated with the contents of the refrigerator decreases, would the entropy of the surroundings need to increase in order for the law of increasing disorder to be obeyed?
Yes. The increase in the entropy associated with the venting of the hot air into the surroundings must be greater than the decrease in the entropy of the contents of the refrigerator.
What is the likelihood that the gases would gain the order they had if we left the system alone for a long time?
There is virtually no chance the gases would spontaneously unmix
Why do natural unsaturated fats have a lower solidification temperature than saturated fats?
They have curved hydrocarbon tails keeping individual molecules farther apart.
Pure aluminum metal has a melting temperature at 660 °C. The process of liquid aluminum freezing to solid aluminum at this temperature is ___
irreversible
Which type of atom has valence electron states high enough in energy that they overlap with the stacked together molecular oribitals that form the conduction band?
metal
The purpose of the control rods in a nuclear fission reactor is
to absorb neutrons, thus limiting the number of nuclei undergoing fission.
If two nitrogen atoms combine to make N2, what type of bond will exist between them?
triple
It is possible to do work and sort the molecules into their separate containers.
true
