Unit 3

Question 1

What happens to energy transfer when both atoms’ electronegativities are relatively high?

Answer 1

The energy input needed is great. This lessens the magnitude of the electronegativity partial charge distribution. (x(A) - x(B))/(X(AV))

High difference = ionic bond
Low difference = covalent bonding

Question 2

What is the most stable configuration for covalent bonds?

Answer 2

When electrons are delocalized between the two atoms in question.

Question 3

What does it mean when covalent bonds are directional?

Answer 3

It refers to the orientation of atoms when they bond. In essence, the electron fields of covalently bonded atoms are highly directional because the atoms are shared, so they get distorted.

Question 4

Why can’t atoms form giant networks of bonds?

Answer 4

Because each atom is constrained by the amount of bonds it can make, and the high directionality.

Question 5

What factors influence IMF strength?

Answer 5

Polarizability, molecular polarity, and bond polarity

Question 6

Polarizability

Answer 6

The extent to which charge distribution in an atom or molecule is affected by the presence of other charged particles. Inversely related to electronegativity.

Larger molecule = higher polarizability, lower volatility
Smaller molecule = lower polarizability, higher volatility

Question 7

What is the magnitude of polarizability affected by?

Answer 7

The number of electrons and the relative size. Bigger particles mean electrons are further away from nucleus. First refer to the electron quantity of the molecule. A large quanitity of electrons reflects an inability of the nucleus to hold on to the charge dispersion. Think: large surface area = large polarizability

Question 8

Dispersion forces

Answer 8

When two atoms approach each other, attractive/repulsive interactions create a net force that ‘polarizes’ the particles, if only temporarily. This is an ‘induced’ dipole moment. Other name: Van der Waal’s forces - KEY PART OF IMFS FOR NON-POLAR SUBSTANCES

Question 9

Strength of dispersion forces is related to

Answer 9

The product of the polarizabilities of the interacting substances

Question 10

Dipole-dipole forces

Answer 10

IMFs resulting from the presence of permanent dipole moments in molecules, wherein oppositely charged ends of a molecule orient themselves as such to be most attracted - directional bonds

Question 11

What kinds of molecules have dipole-dipole interactions?

Answer 11

Molecules that are polar and have preexisting charges due to a permanent dipole moment

Question 12

Rank these molecules in order of volatility: CCl4, CBr4, CF4

How is volatility related to molecular size?

Answer 12

Since volatility is the ability of a molecule to change state, you can assume that higher volatility means lower change of state points. Simultaneously, a larger molecular size means the hold on outer electrons will be weaker, and polarizability will be greater. Consequently, larger molecules are the least volatile, since they will have stronger IMFs due to the polarizability of its constituents.

Answer: CBr4, CCl4, CF4

Question 13

What does the magnitude of dispersion forces determine?

Answer 13

Among other things, it determines many of a substance’s physical properties, like melting/boiling point, surface tension, and viscosity.

(0.05-40 kJ/mol)

Question 14

Why are dipole-dipole forces ‘directional’?

Answer 14

Since the IMF is created on the basis of electrostatic forces of one molecule interacting with those of another, their strength depends on the orientation of the interacting particles.

(5-40 kJ/mol), but less than 20% of total IMFs

Question 15

Hydrogen bonding

Answer 15

IMFs created on the basis of bond polarity, where Hydrogen atoms are covalently bonding to Nitrogen, Oxygen, or Fluorine atoms, and another N, O, or F atom

This results from a large difference in the electronegativities of the respective molecules involved in interactions.

(10-40 kJ/mol) = strongest IMF

directionally oriented bond

Question 16

How many different configurations/arrangments can H bonding occur?

Answer 16

Considering how few molecules can be involved, there are very few. However, once an interaction is created, the molecules will likely stay together unless enough energy is provided to break these bonds.

Question 17

How does branching affect IMFs?

Answer 17

Branching is highly situational. While straighter and longer molecules have more surface area with which to bond to other molecules, longer branching polymers can cause higher levels of entanglement, increasing viscosity and boiling/melting points.

Question 18

What two factors is miscibility dependent on?

Answer 18

1. The relative strength of the particles bonding to themselves, then to each other. The particles will adopt a state where the IMFs are strongest, representing lower PE.
2. # of configurations, wherein the particles adopt a state of higher configurations.

Question 19

Dipole-induced dipole interactions

Answer 19

IMF where a non-polar molecule is polarized by the presence of a polar molecule.

Question 20

Ion-induced dipole

Answer 20

IMF where a non-polar molecule is polarized by the presence of an ionic compound

Question 21

Ion-dipole

Answer 21

IMF where a polar molecule interacts with an ionic compound

Question 22

Macromolecules

Answer 22

Large substances that have properties dependent on their functionality and the structure at different scales

Question 23

Monomers

Answer 23

Repeating unit structures that bond to create polymers/macromolecules

Question 24

[] (sub n)

Answer 24

Inside the brackets is the structure of the monomer, subscript represents how many monomers there are.

Question 25

How can we predict physical properties of a substance?

Answer 25

Analyze the composition, structure, and functional groups of the substance - IMFs may be present, and have a high impact on the properties of the substance

Question 26

Polyamides

Answer 26

Carboxylic acid and amine groups create a rugged and strong substance

Question 27

Polyesters

Answer 27

Carboxylic acid and alcohol groups

Question 28

How does the length of the macromolecule and presence of branching affect shape?

Answer 28

It effects the efficacy of IMFs. Short branching means less entanglement, so weaker IMFs.

Question 29

Saturated fats

Answer 29

Fats which are ‘saturated’ with hydrogen molecules, and thus have no double bonds, making it a straight molecule. Therefore, IMFs are stronger, and they have high melting points.

Question 30

Unsaturated fats

Answer 30

Fats which contain double bonds between Carbon molecules, creating a bent structure in the tail section of the lipid. This weakens the IMFs.

NOTE: the presence of multiple double bonds further lowers melting point because the structure is more and more bent.

Question 31

How does length of fatty acid related to melting point?

Answer 31

Since longer carbon chains mean molar mass, there are also more IMFs present, meaning longer molecules have higher melting points.

Question 32

How does branching affect viscosity?

Answer 32

Short branched molecules have low viscosity, while longer branched molecules have higher viscosity because the branches cause them to get tangled easier.

Question 33

Protein

Answer 33

A monomer-based structure composed of amino acids, which contain a central carbon attached to an amine group, a carboxyl group, an R group side-chain that determines the identity of the monomer, and a single Hydrogen atom

Question 34

Low-density Polyethylene vs high-density polyethylene

Answer 34

Low density Polyethylenes are highly branched, thus making them more weakly bonded together, causing the melting point to be lower. However, high density polyethylenes are flatter and straighter, meaning the IMFs are much stronger, creating a high boiling point.

Question 35

How is potential energy affected by the presence of interactions of similar strength?

Answer 35

It is lowered. Like with like - i.e. induced dipole-induced dipole, dipole-ion, dipole-dipole

Question 36

What do longer hydrocarbon chains do for a fat?

Answer 36

Since there is more surface area, it means there is more room for IMFs to take place, which raises the melting point.

Question 37

Ionic compounds

Answer 37

Result from the combination of metal and nonmetal atoms - larger difference of electronegativities between these two atoms

Question 38

The larger the electronegativity difference between bonding atoms, the more ______ the bond.

Answer 38

Polar

Question 39

If the EN difference >2, what happens to the bonding electrons?

Answer 39

They spend their time closer to the nonmetal atom, leading to an ionic bond.

Question 40

What is the most stable solid-state structure of ionic compounds?

Answer 40

Crystal lattice

Question 41

How does temperature affect the structure of ionic compounds?

Answer 41

It stabilizes the properties of the substance by solidifying it into the crystal lattice form

Question 42

Are electrons fully transferred to the more electronegative atom?

Answer 42

No, but it’s really close considering the electronegativity differences. Consider the ionic character.

Question 43

Ionic compound naming (simple)

Answer 43

metal name + (nonmetal name & -ide)

*add roman numerals if necessary

Question 44

Hydrate naming

Answer 44

Metal name + (nonmetal & -ide) + (prefix & hydrate)

Question 45

Hydroxide

Answer 45

OH-

Question 46

Nitrate

Answer 46

NO3-

Question 47

Carbonate

Answer 47

CO3(2-)

Question 48

Sulfate

Answer 48

SO4(2-)

Question 49

Phosphate

Answer 49

PO4(3-)

Question 50

Ammonium

Answer 50

NH4+

Question 51

Peroxide

Answer 51

O2(2-)

Question 52

-ate vs -ite

Answer 52

‘ate’ compounds have one more oxygen than ‘ite compounds’, but maintain the same charge

Question 53

Face-centered cubic structure

Answer 53

Ions occupy the corners and center of each face of the cube

Question 54

Body-centered cubic

Answer 54

Ions of the same charge occupy only the corners, while opposite charge is at the direct center of the cube

Question 55

True or false: cations are smaller than anions

Answer 55

True: because cations are losing electrons, it vacates the outer shells, decreasing electron repulsion and pulling electrons in towards the nucleus.

Question 56

Coulomb’s Law

Answer 56

Tells us the relative strength of the bond between ions

Higher charges or smaller ions = higher electrostatic forces

F = K(q1)(q2)/(r^2)

r = distance between bonded particles
(q1 and q2) = charges of atoms involved
K = Coulomb’s constant (8.9 x 10^9 Nm2/C2)

Question 57

Why are ionic compounds not conductors when solid?

Answer 57

The electrons in an ionic compound are ‘localized’ to an ion based on polarizability and electronegativity differences. In the molten state, the heat overcomes the strength of the bonds, allowing the electrons to ‘delocalize’ more effectively.

Question 58

What are ‘strong electrolytes’?

Answer 58

Soluble ionic compounds that completely dissociate into free ions when immersed in water

NaCl(s) +H2O(L) => Na+ (aq) + Cl- (aq)

Question 59

What are ‘weak electrolytes’?

Answer 59

Slightly soluble ionic compounds that barely dissociate, and don’t conduct electricity.

Question 60

What is solubility of ionic compounds determined by?

Answer 60

1. Net interactions between ions and water molecules should be stronger than net interactions between the ions themselves. (mixed/dissolved has lower PE)
2. The number of configurations that the ions and water molecules can adopt when mixed is larger than the total number of configurations they can have if they do not mix. (mixed/dissolved has more configurations)

If only one of these conditions is met, the outcome will depend on which competing factor is dominant. Solubility varies with temperature.

Question 61

Why are smaller charges more favorable for dissolution?

Answer 61

Small charges don’t generally constrain the configurations that surrounding water molecules can adopt.

Question 62

How does ion size affect solubility?

Answer 62

Larger ions are more soluble, as demonstrated by Coulomb’s Law. Though larger ions may be less attracted to water molecules, the large size increases the amount of configurations the ion can occupy. Simultaneously, as ion size gets larger, ions requires less energy to dissociate.

Ion- H2O dipole IMFs are dominant

Question 63

Why are insoluble compounds in solution poor conductors?

Answer 63

Because very few of the ions have dissociated, charge is not distributed across the system.

Question 64

Product rule

Answer 64

If the ion charges of each ion have a product of less than 4, then the compound is soluble in water.

Question 65

Components of amino acids

Answer 65

Central carbon bonded to carboxyl group and amine group, a hydrogen, and an R group that determines its identity - about 20 of them