OZ

Question 1

how can a covalent bond become polar

Answer 1

if there is a difference in electronegativity between the two atoms. the bigger the difference in electronegativity the more polar the bond will be

Question 2

how are instantaneous dipole-induced dipoles formed

Answer 2

when a molecule’s electrons shift to one side one side will be slightly delta negative. when this molecule goes near another molecule, the new molecule will also have a delta positive and negative. when these two molecules move away from each other, the dipole is destroyed

Question 3

permanent dipole-permanent dipole

Answer 3

occurs when there is a polar molecule, so a difference in electronegativity between the two atoms. eg HCL

Question 4

hydrogen bonding

Answer 4

strongest type of intermolecular bonding. occurs when hydrogen on one molecule bonds with a nitrogen, oxygen or fluorine (3 most electronegative elements).

Question 5

define rate of a reaction

Answer 5

change of concentration/ amount of a reactant or product per unit time

Question 6

activation energy

Answer 6

minimum amount of energy required for a reaction to occur

Question 7

in a maxwell-boltsmann graph, what are the two axis?

Answer 7

.number of particles = y axis
.kinetic energy = x axis

Question 8

what happens to the particles when you increase heat

Answer 8

.more collisions occur as particles have more kinetic energy

.larger proportion of molecules have the minimum activation energy required to react

Question 9

what affects rate of reaction (apart from temperature)

Answer 9

pressure - particles are closer together so more frequent collisions
concentration - greater quantity of particles so collisions are more frequent

Question 10

homogenous catalyst

Answer 10

catalyst that is the same state as reactants

Question 11

how can rate be measured experimentally

Answer 11

1. use white paper and place a cross on it
2. time how long it takes for precipitate to form (how long it takes for white cross to disappear)

. you can also measure rate of reaction of gas by timing how long it takes for gas to be produced using a gas syringe

Question 12

what are haloalkanes

Answer 12

alkanes with a halogen (s) attached to it

Question 13

boiling trends in haloalkanes and why

Answer 13

increase down the group because of the increasing number of electrons - more idid, meaning the strength of the intermolecular bond is greater

Question 14

nucleophile

Answer 14

electron pair donor, eg H20, ammonia, OH-

Question 15

nucleophilic substitution

Answer 15

when an electron pair donor (eg OH-) displaces an electrophile in a compound through substitution.

Question 16

haloalkane reactivity

Answer 16

increases as you go down the group

Question 17

heterolytic fission

Answer 17

bond breaks and electrons are distributed unequally to form 2 different ions (cation and anion)

Question 18

homolytic fission

Answer 18

bond breaks with the pair of electrons in the bond being shared equally to form two uncharged radicals

Question 19

initiation reaction

Answer 19

radicals are produced using uv light or visible light. the bond breaks homolytically

Question 20

propagation reaction

Answer 20

chain reaction where a radical reacts with a non radical. new radicals are created and go on to react with other non radicals

Question 21

termination reaction

Answer 21

two radicals reacting to form a non radical, thus ending the chain reaction.

Question 22

how is bromomethane made from a free radical substitution

Answer 22

. initiation - two bromine radicals formed
. propagation - bromine radical reacts with CH3 molecule to produce CH3 radical - this new radical reacts with a BR2 molecule forming bromomethane and a bromine radical. this new bromine radical can react with another CH3 molecule
. termination - two radicals react to form a non radical eg bromomethane

Question 23

what is a CFC

Answer 23

molecules that have had all their hydrogens replaced by fluorine and chlorine. they are stable molecules but are broken down by uv.

Question 24

how is ozone formed

Answer 24

.ozone is formed when uv radiation from the sun hits oxygen molecules in the stratosphere (upper level of atmosphere).
. UV is absorbed by O2 molecules to form O radicals
. these O radicals react with O2 molecules to form O3

Question 25

how is ozone broken

Answer 25

the O3 can react with uv radiation (hv) to form O2 and O. this O2 and O can react again to reform ozone - it is a reversible reaction

Question 26

what is photchemical smog

Answer 26

when there is a mix of carbon particulates and ozone

Question 27

affects of photchemical smog and ozone on wildlife

Answer 27

.photchemical smog harms respiratory system in animals and damages plants

.ozone is toxic to humans

Question 28

equation linking energy, wavelength, plancks constant and speed of light

Answer 28

E = (hc) / wavelength
e = energy in j
h= plancks constant
c = speed of light
wavelength = metres