Class Two

Question 1

how to calculate formal charge

Answer 1

FC = V - ½ B - L

Question 2

what is bond length

Answer 2

the distance between 2 nuclei that are bonded to one another

Question 3

what is bond dissociation energy

Answer 3

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

Question 4

heterolytic bond cleavage aka dissociation

Answer 4

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

Question 5

the higher the bond order..

Answer 5

the shorter and stronger the bond

Question 6

the longer the bond..

Answer 6

the weaker it is

Question 7

the shorter the bond..

Answer 7

the stronger it is

Question 8

what is a covalent bond

Answer 8

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

electrons are shared by both atoms to complete octets

Question 9

when is a bond polar

Answer 9

when the electron density between two nuclei are uneven

Question 10

when is a bond non polar

Answer 10

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

Question 11

what is a coordinate covalent bond

Answer 11

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

Question 12

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

Answer 12

lewis base (nucleophile)

Question 13

a lewis base must have..

Answer 13

a pair of nonbonding electrons

Question 14

what is an ionic bond

Answer 14

gaining/losing of electrons

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

Question 15

basis of VSEPR theory

Answer 15

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

Question 16

what is a sigma bond

Answer 16

a bond with 2 electrons that are localized between 2 nuclei

Question 17

what is a pi bond

Answer 17

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

Question 18

if a molecule contains no polar bonds..

Answer 18

it cannot be polar

Question 19

what are intermolecular forces

Answer 19

the relatively weak interactions that take place between neutral molecules

Question 20

ion dipole forces

Answer 20

polar molecules attracted to ions

Question 21

dipole dipole forces

Answer 21

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

Question 22

what is the strongest dipole dipole force

Answer 22

hydrogen bonding

Question 23

dipole induced dipole force

Answer 23

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

Question 24

London dispersion force

Answer 24

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

Question 25

characteristics of London dispersion forces

Answer 25

very weak

Question 26

substances with higher intermolecular forces have..

Answer 26

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

Question 27

what are van Der Waals forces

Answer 27

dipole forces, hydrogen bonding and London forces

Question 28

criteria for a hydrogen bond to form

Answer 28

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

Question 29

what is vapour pressure

Answer 29

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

Question 30

intermolecular forces and vapour pressure relationship

Answer 30

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

Question 31

volatile liwuids

Answer 31

easily vaporized liquids (high vapour pressures)

Question 32

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

Answer 32

boiling point

Question 33

what is an ionic solid

Answer 33

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

Question 34

what is a network solid

Answer 34

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)

Question 35

what is a metallic solid

Answer 35

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

Question 36

why are metals good conductors of heat

Answer 36

due to their conduction electrons - free to move around

Question 37

what is a molecular solid

Answer 37

held together by hydrogen bonds, dipole-dipole forces or London forces (intermolecular forces) weaker → lower melting and boiling points often liquids or gases

Question 38

what is a chelate

Answer 38

ligand that donates multiple lone pairs

Question 39

strongest intermolecular force

Answer 39

ion-dipole force

Question 40

dipole induced dipole interactions occur between..

Answer 40

a polar and non polar molecule

Question 41

which intermolecular force is seen with all molecules

Answer 41

London forces

Question 42

what is thermodynamics

Answer 42

the transformation of energy from one from to another

Question 43

zeroth law of thermodynamics

Answer 43

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

Question 44

thermal equilibrium and temperature

Answer 44

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

Question 45

first law of thermodynamics

Answer 45

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

Question 46

when energy flows into a system from the surroundings..

Answer 46

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

Question 47

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

Answer 47

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

Question 48

what is enthalpy

Answer 48

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

Question 49

when a bond is formed..

Answer 49

energy is released → enthalpy is negative

Question 50

enthalpy of a reaction =

Answer 50

H_products - H_reactants

Question 51

another name for the enthalpy change of a reaction

Answer 51

heat of reaction

Question 52

what are standard conditions

Answer 52

298 K (25 C) pressure = 1 atm solutions = conc of 1 M

Question 53

what is the standard heat of formation

Answer 53

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

Question 54

standard heat of formation of elements in their natural form

Answer 54

zero

Question 55

what does a positive standard heat of formation mean

Answer 55

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

Question 56

what does a negative standard heat of formation mean

Answer 56

making that compound from its elements gives off energy

Question 57

Hess's law of heat summation

Answer 57

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

Question 58

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

Answer 58

the sign for enthalpy is reversed too

Question 59

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

Answer 59

then the enthalpy must be multiplied by the same number

Question 60

to break a bond..

Answer 60

3energy is needed

Question 61

in making a bond..

Answer 61

energy is released

Question 62

second law of thermodynamics

Answer 62

disorder of the universe increases in a spontaneous process

Question 63

change of entropy equation =

Answer 63

S_products - S_reactants

Question 64

if randomness increases, or order decreases..

Answer 64

then entropy is positive

Question 65

if randomness decreases, or order increases

Answer 65

then entropy is negative

Question 66

third law of thermodynamics

Answer 66

absolute zero = zero entropy entropy of a pure substance at zero temperature = zero

Question 67

Gibbs free energy

Answer 67

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

Question 68

Gibbs free energy formula

Answer 68

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

Question 69

if G is less than O..

Answer 69

reaction is spontaneous in the forward direction

Question 70

if G = 0..

Answer 70

reaction is at equilibrium

Question 71

if G is greater than 0..

Answer 71

the reaction is non spontaneous in the forward direction