Chem 1331 > Final Exam > Flashcards

Final Exam Flashcards

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1
Q

When looking at an abundance vs. atomic mass graph, how can you tell what the most abundant isotope is?

A

It will be the tallest bar on the graph

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2
Q

True or False: The abundance vs. atomic mass graph shows the weight of one atom?

A

True - the periodic table only shows the molar mass, not the mass of one atom. For example, Boron’s graph shows a bar at 10 and a bar at 11. Boron could either have a mass of 10 for one atom or a mass of 11 for one atom.

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3
Q

How do you determine if the most abundant isotope on the abundance vs. atomic mass graph has more neutrons?

A

Take the most abundant atomic mass number and subtract the element’s number of protons from it.
Example: Boron has 11 as the most abundant mass, so 11 - 5 = 6 neutrons.

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4
Q

True or False: Can an atom have 80% 6 neutrons and 20% 5 neutrons?

A

FALSE!! Only 100%’s (like the score that I’m going to get on this exam)

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5
Q

Which has more atoms? One mole of Carbon or one mole of Hydrogen?

A

They will have the same amount.
One mole WILL ALWAYS be 6.022 x 10^23 atoms

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6
Q

Which one will have more atoms? One gram of atoms of Carbon or one gram of atoms of Hydrogen?

A

One gram of atoms of Hydrogen.

Because H is lighter, it takes more atoms to reach one gram compared to a heavier element (such as Carbon).

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7
Q

Which one will have more moles of atoms? One gram of moles of atoms of Carbon or one gram of moles of atoms of Hydrogen?

A

One gram of moles of atoms of Hydrogen.

Because H is lighter, it will take more moles of atoms to get to one gram compared to Carbon, a much heavier element.

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8
Q

The closer the charges are for positive energy, the ________ the system is

A

Less stable

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9
Q

No matter the distance, positive energy will _____ become negative

A

NEVER! Positive energy repels and negative energy is only associated with attraction.

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10
Q

Positive energy will ______ repel each other, no matter the distance

A

ALWAYS

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11
Q

Fast and frequent waves are associated with what energy?

A

High energy

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12
Q

Slow waves are associated with what energy?

A

Low energy

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13
Q

High frequency occurs with what energy?

A

High energy

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14
Q

Low frequency occurs with what energy?

A

Low energy

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15
Q

The ground state is….

A

The most stable, lowest possible energy level an atom or molecule can have, where its electrons occupy the closest orbitals to the nucleus.

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16
Q

The ground state of Carbon has how many unpaired electrons?

A

2 - there are two unpaired electrons in the 2p orbital

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17
Q

True or False: Excited state can be written as 1s^2, 2s^2, 2p^2?

A

TRUE - the unpaired electrons can skip “boxes” in the sp^2 orbital and be in the middle box or third box, not the first one.

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18
Q

True or False: 1s^2, 2s^2, 3p^2 is forbidden?

A

FALSE - can be excited state and skip over sp orbital.

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19
Q

True or False: 1s^2, 2s^2, 3f^2 is forbidden?

A

TRUE - there is no such thing as an f orbital.

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20
Q

What happens when a photon emits?

A

It goes from high energy to low energy.

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21
Q

What happens when a photon absorbs?

A

It goes from low energy to high energy.

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22
Q

True or False: The orbitals with high energy will have less negative energy?

A

TRUE - the further they are from the nucleus, the less negative energy they will have.

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23
Q

How many protons are in each of the following: F(-) and F?

A

They will both have 9 protons. Since they are both Fluorine, they will have 9 protons.

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24
Q

How many electrons are in each of the following: F(-) and F?

A

F(-) will have 10 electrons (1 more electron than protons because of the 1- charge) and F will have 9 electrons (neutral).

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25
Does more electrons mean smaller size?
No - more electrons mean BIGGER size. The more electrons there are, the larger the atomic radius is of an element.
26
Does 19F(-) has a larger ionization energy than 19F(+)?
No - 19F(+) has 9 protons and 8 electrons so the electrons are pulled very tightly, making them harder to remove than those in the 19F(-), which has 9 protons and 10 electrons.
27
Does more electrons mean higher zeff?
No - more electrons means a lower zeff because the outer electrons will experience a lower effective nuclear charge (zeff) due to more shielding.
28
Do electrons repel each other? And does that have any effect on the size of an atom?
Yes - electrons repel each other. When this happens, the action of repulsion will increase the size of the atomic radius.
29
Do protons repel each other? And does that have any effect on the size of an atom?
Yes and no - protons do repel each other, but they stay in the nucleus, meaning they are not effecting the atomic radius.
30
If an atom has more electrons, does that make it have a higher electronegativity?
NOPE - they are not related in that sense at all.
31
Does more protons mean a larger zeff? And does that contribute to electronegativity?
Yes and yes - more protons strengthens attraction with electrons, which increases zeff (or effective nuclear charge). Higher zeff means higher electronegativity because there is a stronger pull from the nucleus.
32
True or False: Zeff is increased if the number of protons are decreased?
FALSE - they are proportional. If zeff is increasing, that must mean that the number of protons are increasing. If zeff is decreasing, that must mean that the number of protons are decreasing. More protons creates more attraction, leading to a higher effective nuclear charge (nucleus is more attractive with the stronger "pull").
33
What breaks when a structure melts?
IMF's. NOT BONDS!!!!
34
Can you determine high/low boiling point based on the bond type?
YES - bond type helps determine the strength of intermolecular forces (IMF's).
35
True or False: Covalent bonds can dissociate but ionic bonds cannot?
FALSE - it's the other way around. Covalent bonds cannot dissociate because they're considered "molecular" between molecules whereas ionic bonds are considered a "lattice" of ions. Also, ionic bonds can dissociate because the crystal lattice that they form can be broken by polar molecules, such as water. Water separates the ions, not the covalent bonds within the molecule.
36
Does NH4(+) follow the octet rule?
Yes - it exists as Ammonium. The positive charge allows for the nitrogen to follow the octet rule.
37
Does H3O+ follow the octet rule?
Yes - it exists as Hydronium. The positive charge allows for the oxygen to follow the octet rule in this molecule.
38
What are chiral carbons?
An SP^3 hybridized carbon with 4 DIFFERENT things attached.
39
How many things are attached in an SP hybridizaton?
TWO
40
How many things are attached in an SP^2 hybridization?
THREE
41
How many things are attached in an SP^3 hybridization?
FOUR
42
SP is associated with what angle and structure?
180 degrees AND linear
43
SP^2 is associated with what angle and structure?
120 degrees AND trigonal planar
44
SP^3 is associated with what angle and structure?
109.5 degrees AND tetrahedral
45
When do molecular dipoles cancel out?
- When there is molecular symmetry - Identical terminal atoms
46
What is trigonal pyramidal?
A central atom is bonded to three other atoms and has one lone pair of electrons.
47
True or False: When a bond is part of a resonance structure and has double bond behavior, it will vibrate at a higher frequency compared to a single bond in that same structure.
TRUE - More energy is needed for the double bonds to vibrate.
48
Is a double bond longer than a single bond?
NO - double bonds are shorter than single bonds. Double bonds share electrons, pulling the nuclei closer together, resulting in a shorter bond length and greater strength.
49
True or False: Resonance plays a crucial role in comparing bond length.
TRUE - it modifies standard single/double bond lengths, creating intermediate bond lengths and orders, significantly affecting molecular properties and stability.
50
How does strong bonds relate to wavenumber at which vibrations appear?
Strong bonds mean larger wavenumber at which vibrations appear. Same with vise versa. Weak bonds mean shorter wavenumber at which vibrations appear. All has to do with energy. Strong bonds require more energy, meaning they vibrate at higher a wavenumber/frequency than weaker bonds that require little to no energy.
51
How does light vs heavy bonds play a role in frequency/wavenumber with vibration?
Lighter bonds will vibrate at a higher frequency due to the fact that they can be considered "light spring masses" and will vibrate more frequently than heavier ones, that will vibrate at a lower frequency, due to the fact that the mass is so different.
52
What does electronegativity have to do with wavenumber?
Absolutely nothing!
53
True or False: Most non-polar structures are not soluble in water?
TRUE - because of the "like dissolves like" rule, and because water is a POLAR molecule, it will not want to dissolve non-polar molecules because those are not "like" polar molecules.
54
When two amino acids form a peptide bond, what functional group is formed?
An amide functional group. The double bonded oxygen to the carbon that is connected to the nitrogen is the amide functional group.
55
When two amino acids form a peptide bond, does a new chiral center form?
NO - it does not create a new one, but it links their existing chains of chiral centers together (if there are any).
56
True or False: A carboxylic functional group disappears when two amino acids form a peptide bond?
TRUE - you take out the O-H bond at the end of the carboxylic functional group and replace that with the new amino acid, starting with the N-H.
57
True or False: Hydrogen bonds are stronger than London Dispersion Forces?
TRUE - Hydrogen bonds are the strongest out of the IMF's (except for Ion-Dipole, but this question is not asking that). It typically goes Hydrogen Bonds > Dipole-Dipole > London Forces.
58
What is the IMF that is stronger than Hydrogen bonds?
Ion-Dipole - this IMF involves an interaction between a full electric charge from an ion and a partial charge on a polar molecule. Compared to hydrogen bonding, the strongest part of their bond is the highly electronegative atom (N, O, or F) and another nearby electronegative atom. The full charge on the ion-dipole is what makes it the strongest.
59
Does the mass of the molecule impact the strength of the IMF?
YES - especially London Dispersion Forces, as the higher the mass is, the stronger the overall attraction is. This increases the boiling/melting points. However, specific strong forces, such as hydrogen bonds, can "override" this trend, which is why it is most likely London Dispersion Forces that follow this.
60
The enthalpy of condensation is a _______ (negative/positive) value because the process is _________ (exothermic/endothermic).
Negative, exothermic. We go from gas to liquid. Gas is in a higher state than liquid, so we are going "down" or "backwards" in this phase change, meaning we do not need to put energy into this process. Instead, the energy comes out (exothermic).
61
When you mix two beakers that have the same amount of liquid water but at different temperatures, what happens?
They will exchange heat until they reach equilibrium. The heat that one gains is the heat that the other loses.
62
What happens with the water temperature as ice melts?
The water temperature will decrease until its at equilibrium with that of ice.
63
Ice has a ______ (lower/higher) heat capacity than water.
Lower - liquids typically have higher heat capacities, due to the molecules having more freedom to move, vibrate, and rotate, which allows them to store more heat before temperature rises significantly, whereas solids are "frozen" and can only vibrate (absorb the heat much faster).
64
Does the heat capacity of ice play a huge role in deciding the final temperature of mixing two beakers with the same volume, but different temperatures?
YES - because ice has a lower heat capacity (meaning it changes temperature faster) and the final temperature is closer to the initial temperature of water than ice. In these questions, look out for final temp. and initial temp.
65
When given two structures with two different heat capacity numbers, which one will take more time to heat up one mole of it?
The one with the larger number. Bigger number = higher heat capacity, meaning it will take more time to heat up any amount of it, compared to a smaller number (lower heat capacity) with the same amount.
66
True or False: Intermolecular Forces is the main contributor to heat capacity?
FALSE - the number of bonds a structure has is the main contributor, not IMF's. Essentially, each bond introduces additional "degrees of freedom" (ways to store energy), specifically vibrational modes. So, the more bonds a structure has, the more energy it can store, making it have a larger heat capacity.
67
When given two structures with two different heat capacity numbers, which one will increase its temperature the most when a certain amount of joules of heat is added to both?
The one with the smaller heat capacity number. Smaller heat capacity means that it will change temperature the easiest, because it has little-to-no ways of storing the heat compared to structures with a higher heat capacity number.
68
True or False: The deciding role when comparing two compounds and their vapor pressure and liquid-gas equilibrium is mass.
FALSE - mass does play a role, but the MAIN DECIDING ROLE is going to be IMF's. They dictate how easily molecules can escape the liquid phase; stronger IMFs (like hydrogen bonds) hold molecules together tightly, requiring more energy to break free, leading to lower vapor pressure, while weaker IMFs (like London dispersion forces) allow easier escape, resulting in higher vapor pressure, making IMFs more crucial than just mass, although mass influences IMFs.
69
The stronger the IMF's, the _____ (more/less) _______ (positive/negative) the enthalpy of condensation.
more, negative. Stronger IMF's take more energy and condensation will always be a negative value (going from Gas to Liquid).
70
Which of the following will increase when dissociating an ionic substance in water? - Boiling Point - Freezing Point - Vapor Pressure
Only boiling point will increase. This is called "boiling point elevation," which basically means that the ions increase the number of solute particles, which lowers the waters vapor pressure and requires more energy (higher temperature) to boil.
71
Which of the following will decrease when dissociating an ionic substance in water? - Boiling Point - Freezing Point - Vapor Pressure
Freezing point AND Vapor pressure. - Freezing point decreases due to a phenomenon called "freezing point depression" because the ions disrupt water's ability to form ice crystals, and more particles (ions) means a greater depression. This is why salt (NaCl) is used to de-ice the roads... it creates more particles, causing the water to freeze at much lower temperatures. - As for vapor pressure, it is just opposite of boiling point. If boiling point is increasing, than vapor pressure must be decreasing. They are inversely proportional.
72
Hydrogen bonds are ______ (weaker/stronger) than ion-dipole interactions?
WEAKER
73
True or False: Solute-Solvent interactions are stronger than Hydrogen Bonds.
TRUE - Because ion-dipole interactions are stronger than Hydrogen bonds, so water interacts with ions (ion-dipole) instead of water molecules (in hydrogen bonds).
74
Fill in the blanks: _______ dissolves ______.
Like, like. This is used with dissociation and solubility. For instance, polar molecules (like water) only dissolves things that are like it. Same goes for non-polar. Non-polar likes non-polar.
75
Which dissolves better in hexane: methanol or pentanol?
Pentanol. Hexane is a large chain of non-polar molecules. Even though pentanol has some polarity in it, it has a longer chain of non-polar than methanol.
76
What trend(s) go increasing down and to the left?
Atomic Radius The elements with the largest atomic radius' will be found in the bottom left corner of the periodic table. Examples include Rubidium and Barium.
77
What trend(s) go increase up and to the right?
Ionization Energy and Zeff (effective nuclear charge). Examples include Chlorine, Argon, and Fluorine.
78
What are the exceptions to the ionization energy to effective nuclear charge trend?
2A > 3A and 5A > 6A
Chem 1331
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