Class Two Flashcards

1
Q

how to calculate formal charge

A

FC = V - ½ B - L

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2
Q

what is bond length

A

the distance between 2 nuclei that are bonded to one another

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3
Q

what is bond dissociation energy

A

the energy required to break the bond homolytically (one electron of the bond being broken goes to each fragment of the molecule)

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4
Q

heterolytic bond cleavage aka dissociation

A

both electrons of the electron pair that make up the bond end up on the same atom → forms an anion and a cation

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5
Q

the higher the bond order..

A

the shorter and stronger the bond

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6
Q

the longer the bond..

A

the weaker it is

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7
Q

the shorter the bond..

A

the stronger it is

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8
Q

what is a covalent bond

A

formed between twos when each contributes one or more of its unpaired valence electrons

electrons are shared by both atoms to complete octets

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9
Q

when is a bond polar

A

when the electron density between two nuclei are uneven

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10
Q

when is a bond non polar

A

when the electron density between the two nuclei is even (little to no difference in electronegativity)

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11
Q

what is a coordinate covalent bond

A

when one atom donates both of the shared electrons in a bond

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12
Q

when an atom gives the electrons in a coordinate covalent bond, it acts as a..

A

lewis base (nucleophile)

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13
Q

a lewis base must have..

A

a pair of nonbonding electrons

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14
Q

what is an ionic bond

A

gaining/losing of electrons

held together by the electrostatic attraction between a cation and an anion

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15
Q

basis of VSEPR theory

A

electrons repel each other therefore they try to move as far apart as possible

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16
Q

what is a sigma bond

A

a bond with 2 electrons that are localized between 2 nuclei

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17
Q

what is a pi bond

A

composed of 2 electrons that are localized to the region that lies on opposite sides of the plane

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18
Q

if a molecule contains no polar bonds..

A

it cannot be polar

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19
Q

what are intermolecular forces

A

the relatively weak interactions that take place between neutral molecules

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20
Q

ion dipole forces

A

polar molecules attracted to ions

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21
Q

dipole dipole forces

A

attractions between the positive end of one polar molecule and the negative end of another polar molecule

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22
Q

what is the strongest dipole dipole force

A

hydrogen bonding

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23
Q

dipole induced dipole force

A

a permanent dipole in one molecule inducing a dipole in a neighbour non polar molecule for a moment

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24
Q

London dispersion force

A

instantaneous dipole in a non polar molecule can induce a dipole in a neighbour non polar molecule

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25
Q

characteristics of London dispersion forces

A

very weak

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26
Q

substances with higher intermolecular forces have..

A

higher melting/boiling points, greater viscosities and low vapour pressures

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27
Q

what are van Der Waals forces

A

dipole forces, hydrogen bonding and London forces

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28
Q

criteria for a hydrogen bond to form

A

molecule have covalent bond between H and either N, O or F

another molecule must have a lone pair of electrons on an N, O or F atom

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29
Q

what is vapour pressure

A

the pressure exerted by the gaseous phase of a liquid that is exported from the exposed surface of the liquid

30
Q

intermolecular forces and vapour pressure relationship

A

the weaker the intermolecular forces, the high its vapour pressure (easily evaporates)

31
Q

volatile liwuids

A

easily vaporized liquids (high vapour pressures)

32
Q

the vapour pressure of a substance is indirectly related to..

A

boiling point

33
Q

what is an ionic solid

A

a solid held together by the electrostatic attraction between cations and anions in a lattice structure

34
Q

what is a network solid

A

atoms are connected in a lattice of covalent bonds

intermolecular forces are identical to intramolecular forces (like an ionic solid)

very strong and hard solids at room temp (e.g. diamond)

35
Q

what is a metallic solid

A

covalently bond lattice of nuclei and their inner shell electrons, surrounded by conduction electrons (free to move throughout the lattice)

36
Q

why are metals good conductors of heat

A

due to their conduction electrons - free to move around

37
Q

what is a molecular solid

A

held together by hydrogen bonds, dipole-dipole forces or London forces (intermolecular forces)

weaker → lower melting and boiling points

often liquids or gases

38
Q

what is a chelate

A

ligand that donates multiple lone pairs

39
Q

strongest intermolecular force

A

ion-dipole force

40
Q

dipole induced dipole interactions occur between..

A

a polar and non polar molecule

41
Q

which intermolecular force is seen with all molecules

A

London forces

42
Q

what is thermodynamics

A

the transformation of energy from one from to another

43
Q

zeroth law of thermodynamics

A

if two systems are both in thermal equilibrium with a third system, then the two initial systems are in thermal equilibrium with one another

44
Q

thermal equilibrium and temperature

A

if two systems are in thermal equilibrium, they have the same temperature

45
Q

first law of thermodynamics

A

the total energy of the universe is constant - energy cannot be created or destroyed

46
Q

when energy flows into a system from the surroundings..

A

the energy of the system increase and the energy of the surroundings decreases

47
Q

when energy flows out of a system into the surroundings..

A

the energy of the system decreases and the energy of the surroundings increase

48
Q

what is enthalpy

A

measure of the heat energy that is released or absorbed when bonds are broken/formed during a reaction (constant P)

49
Q

when a bond is formed..

A

energy is released → enthalpy is negative

50
Q

enthalpy of a reaction =

A

Hproducts - Hreactants

51
Q

another name for the enthalpy change of a reaction

A

heat of reaction

52
Q

what are standard conditions

A

298 K (25 C)

pressure = 1 atm

solutions = conc of 1 M

53
Q

what is the standard heat of formation

A

the amount of energy required to make one mole of a compound from its constituent elements in their natural form

54
Q

standard heat of formation of elements in their natural form

A

zero

55
Q

what does a positive standard heat of formation mean

A

input of heat is required to make that compound from its constituent elements

56
Q

what does a negative standard heat of formation mean

A

making that compound from its elements gives off energy

57
Q

Hess’s law of heat summation

A

if a reaction occurs in many steps, the sum of the energies absorbed/given off in all the steps will be the same for the overall reaction

58
Q

Hess’s law: if a reaction is reversed..

A

the sign for enthalpy is reversed too

59
Q

Hess’s law: if an equation is multiplied by a coefficient..

A

then the enthalpy must be multiplied by the same number

60
Q

to break a bond..

A

3energy is needed

61
Q

in making a bond..

A

energy is released

62
Q

second law of thermodynamics

A

disorder of the universe increases in a spontaneous process

63
Q

change of entropy equation =

A

Sproducts - Sreactants

64
Q

if randomness increases, or order decreases..

A

then entropy is positive

65
Q

if randomness decreases, or order increases

A

then entropy is negative

66
Q

third law of thermodynamics

A

absolute zero = zero entropy

entropy of a pure substance at zero temperature = zero

67
Q

Gibbs free energy

A

energy that’s available to do useful work from a chemical reaction

68
Q

Gibbs free energy formula

A

change in G = change in H - (T)(change in S)

69
Q

if G is less than O..

A

reaction is spontaneous in the forward direction

70
Q

if G = 0..

A

reaction is at equilibrium

71
Q

if G is greater than 0..

A

the reaction is non spontaneous in the forward direction