OZ definitions and concepts

Question 1

Dipole

Answer 1

partial charge on an atom caused by differences in electronegativities of atoms in a covalent bond

Question 2

Electronegativity

Answer 2

the ability of an atom to attract to a bonding pair of electrons in a covalent bond

Question 3

Hydrogen bonding

Answer 3

• interaction between a hydrogen atom and an electronegative atom
• the electronegative atom is most commonly, nitrogen, oxygen or fluorine
• the slightly positive hydrogen is attracted to the lone pair on the electronegative atom
• hydrogen bonding is stronger than instantaneous dipole-induced dipole forces and permanent dipole-permanent dipole forces
• hydrogen bonding is weaker than ionic and covalent bonding

Question 4

Intermolecular forces

Answer 4

• forces that act between molecules
• include instantaneous dipole-induced dipole forces, permanent dipole-permanent dipole forces and hydrogen bonding

Question 5

polar bond

Answer 5

• a covalent bond that has a permanent dipole due to differences in the electronegativities of the atoms that make up the bond
• not equal forces

Question 6

Instantaneous dipole-induced dipole

Answer 6

• exist between ALL molecules
• they arise due to fluctuations of electron density
• these fluctuations may temporarily result in an uneven distribution, producing an instantaneous dipole

Question 7

activation enthalpy

Answer 7

minimum enthalpy required for a reaction to occur between two colliding particles

Question 8

amines

Answer 8

compounds that contain the NR3 functional group

Question 9

catalyst

Answer 9

substance that increases the rate of reaction without being chemically changed or used up
they work by providing an alternate pathway with a lower activation energy

Question 10

collision theory

Answer 10

theory that particles must collide with sufficient energy to react

Question 11

effect of concentration on reaction rate

Answer 11

as concentration increases, the reacting particles get closer to there are more frequent successful collisions

Question 12

effect of pressure on rate

Answer 12

as pressure increases, particles get closer together so there are more frequent successful collisions

Question 13

effect of temperature on rate

Answer 13

increasing the temperature increases the kinetic energy in particles so there will be more frequent successful collisions as a larger proportion of the particles will have equal or greater energy than the activation energy

Question 14

enthalpy profile

Answer 14

diagram showing the energy change of a reaction as it moves from reactants to products

Question 15

functional group

Answer 15

atom/group of atoms responsible for the characteristic reactions of a compound

Question 16

haloalkanes

Answer 16

• organic compound made up of a halogen atom and an alkane.
• can be formed from alcohols by substitution reaction with halide ions in the presence of an acid

Question 17

Homogeneous catalyst

Answer 17

catalyst that is in the same phase as the reactants

Question 18

homologous series

Answer 18

series of organic compounds with the same functional group

Question 19

Boltzmann curve

Answer 19

• shows the distribution of the molecular energies in a gas at a constant temperature
• area under the curve indicates the total particles there are

Question 20

nomenclature

Answer 20

naming system for compounds

Question 21

rate of reaction

Answer 21

measure of the amount of product formed or reactant used over time

Question 22

boiling point

Answer 22

temperature at which a compound moves from a liquid state to a gaseous state

Question 23

bond enthalpy

Answer 23

energy required to break one mole of gaseous bonds

Question 24

curly arrow

Answer 24

• shows the movement of a pair of electrons
• must start from a bond, a lone pair of electrons or a negative charge

Question 25

free radical substitution

Answer 25

- a photochemical reaction between halogens and alkanes to form haloalkanes - reaction requires UV - involves the three stages initiation, propagation and termination

Question 26

free radical

Answer 26

a species with an unpaired electron

Question 27

heterolytic fission

Answer 27

when a covalent bond breaks and one bonding atom receives both electrons from the bonded pair

Question 28

homolytic fission

Answer 28

when a covalent bond breaks and each bonding atom receives one electron from the bonding pair forming two radicals

Question 29

initiation

Answer 29

- first step in radical substitution - involves the formation of radicals

Question 30

nucleophile

Answer 30

- atom or molecule that donates an electron pair to form a covalent bond - attracted to electron-deficient areas

Question 31

nucleophilic substitution

Answer 31

- reaction of an electron pair donor (nucleophile) and an electron pair acceptor (electrophile) - involves one species being replaced with another species

Question 32

ozone

Answer 32

- chemically formed in the upper atmosphere - absorbs UV and prevents harmful radiation reaching earth - formed by 3O2 ---UV---> 2O3

Question 33

ozone depletion

Answer 33

chlorine atoms catalyse the decomposition of ozone, destroying the ozone layer

Question 34

partial charges

Answer 34

slight charge on an atom due to the bonded atoms having different electronegativities

Question 35

photodissociation

Answer 35

process where a molecule is broken down using photons

Question 36

propagation

Answer 36

second step in radical substitution where a radical reacts with another species

Question 37

SN2

Answer 37

nucleophilic substitution reaction where the mechanism route used has two compounds in the rate determining step

Question 38

substitution

Answer 38

reaction where one atom/group of atoms is substituted for another atom/group of atoms

Question 39

termination

Answer 39

final step in radical substitution where two radicals react together to form a species that only has paired electrons

Question 40

ozone as sunscreen

Answer 40

ozone blocks UV so is a natural sunscreen

Question 41

pollution effect on ozone

Answer 41

man made pollutants thin the ozone layer, so it doesn't absorb as much UV radiation in those areas

Question 42

electromagnetic spectrum

Answer 42

range of frequencies of electromagnetic radiation and the respective wavelengths

Question 43

electron promotion

Answer 43

when an electron absorbs a photon and moves from a low energy orbital to a vacant higher energy orbital

Question 44

infrared

Answer 44

area of electromagnetic spectrum that has wavelengths between 780nm and 1mm

Question 45

UV

Answer 45

area of electromagnetic spectrum that has wavelengths between 10nm and 400nm

Question 46

visible light

Answer 46

area of electromagnetic spectrum that has wavelengths between 380 and 700nm