Ozone

Question 1

Calculating % composition- ppm

Answer 1

• Divide no. of molecules by 1,000,000

- Multiply answer by 100

Question 2

Calculating conc. in ppm

Answer 2

Multiply % by 10,000

Question 3

Equation for wave theory

Answer 3

speed of light c (ms-1) =wavelength (m) x frequency v (s-1)

Question 4

Equation for particle model

Answer 4

Energy E (J) = Planck constant h ( J s) x frequency v (s-1)
* if you're asked to calculate an energy value per mole of photon remember to multiply the value by the Avagadro constant

Question 5

What happens when radiation interacts with matter?

Answer 5

• The electromagnatic radiation transfers energy to the chemicals involved. This causes changes in the chemical depending on the chemical and amount of energy

Question 6

Name the different types of energy association behaviors

Answer 6

• Translation (molecule moves around as a whole)
• Rotation (whole molecule)
• Vibration of bonds
• Electron energy

Question 7

The order of increasing energy of the different energy behaviors

Answer 7

translational energy < rotational energy < vibrational energy < electronic energy

Question 8

Why do the have different energy changes?

Answer 8

Its because different energy changes correspond to different parts of the spectrum

Question 9

What electronic changes occur when a molecule absorbs UV radiation?

Answer 9

Excitation:

• Ionisation (lose of electrons)
• Dissociation (photodissociation- radicals formed)
• Release of energy

Question 10

What are radicals?

Answer 10

Molecules or atoms with at least one unpaired electron- no overall charge

Question 11

What is Bond fission?

Answer 11

Bond breaking and involves the redistribution of the electrons

Question 12

What are the two types of bond fission?

Answer 12

Homolytic & heterolytic fission

Question 13

What is heterolytic fission?

Answer 13

Both shared electrons go to just one of the atoms. Common when a bond is polar

Question 14

What is homolytic fission?

Answer 14

One of the shared electrons goes to each atom. Produces radicals - non polar bonds

Question 15

Ozone production

Answer 15

Reaction 1: O2 + hv = O + O
Reaction 2: O + O2 = O3
Reaction 3: O + O3 = O2 + O2

Question 16

What is the Initiation, propagation & termination reaction?

Answer 16

Initiation - Radicals are formed
Propagation- Radicals as reactants and products
Termination - Two radicals collide and remove the radicals

Question 17

Equation for rate of reaction

Answer 17

rate of reaction = change in property / time taken

Question 18

Different ways of measuring the rate of reaction

Answer 18

• Measuring vol. of gas
• Measuring mass change
• pH measurement
• Colorimetry - chnage in colour
• Chemical analsyis

Question 19

Describe the Chemical analysis process

Answer 19

Involves taking samples of reaction mixture at regular intervals and stopping the reaction before analysis.
The rest can be determined by titration

Question 20

What affects the rate of a reaction?

Answer 20

• Conc. of the reaction / pressure
• Temperature
• Intensity of radiation
• Particle size / surface area
• Catalyst

Question 21

Define activation enthalpy

Answer 21

The minimum kinetic energy required by a pair of colliding particles before a reaction will occur.

Question 22

What is the Maxwell-Boltzmann distribution?

Answer 22

Defines the distribution of kinetic energies in a gas at a given temperature.

Question 23

Define homogeneous catalyst

Answer 23

Catalysts that are in the same physical state as the reactants- work by forming an intermediate compound with the reactants.
* the enthalpy change is the same for the catalysed & uncatalysed reactions.

Question 24

Catalysts and equilibrium

Answer 24

Catalysts don’t affect the position of equilibrium, they only ALTER the RATE at which the equilibrium is attained not the COMPOSITION.

Question 25

How do Chlorine and bromine atoms deplete ozone?

Answer 25

Reaction 1: Cl + O3 = ClO + O2 Reaction 2: ClO + O = Cl + O2 Overall reaction : O + O3 = O2 +O2 *Cl & Br acts as catalysts as they aren't used in both reactions.

Question 26

Name the other radicals that also remove ozone

Answer 26

- Hydroxyl radical & nitrogen monoxide | * NO & NO2 are both radicals but not highly reactive -relatively stable

Question 27

Define polar bonds

Answer 27

Atoms attracting bonding electrons unequally - difference in electronegativity

Question 28

Define electronegativity

Answer 28

Electronegativity is a measure of the ability of an atom in a molecule to attract electrons in a chemical bond to itself

Question 29

Increase in electronegativity along periods & groups

Answer 29

``` Groups: 1 < 2 < 3 < 4 < 5 < 6 < 7 Periods: 5 < 4 < 3 <2 < 1 * The closer to fluorine the more electronegative. ```

Question 30

Define inter molecular bonds

Answer 30

Cause molecules to be attracted to each other- strength of bonds indicates the boiling point.

Question 31

Define dipole

Answer 31

A molecule with both a positive & negative end. | * Molecular dipoles depend on electronegativity differences and shape of molecule (symmetry

Question 32

Cause of permanent dipole

Answer 32

Occur when two atoms in a bond have substantially different electronegativities.

Question 33

Cause of Instantaneous dipole

Answer 33

When electrons within a molecule are in constant motion

Question 34

Cause of Induced dipole

Answer 34

Unpolarised molecule is next to a dipole, the dipole attracts or repels electrons in the unpolarised moecule inducing it.

Question 35

Name the three types of intermolecular bonds

Answer 35

- Instantaneous - induced dipole (weakest - non polar substances) - Permanent -permanent dipole (relatively strong - liquids & solids) - Permanent- induced dipole * In halogens,the smaller the atom the weaker the instantaneous- induced dipole

Question 36

Hydrogen bonding

Answer 36

Strongest type of intermolecular bond- permanent-permanent dipole

Question 37

Define substitution reaction

Answer 37

A reaction in which one atome or group in a molecule is replaced by another atom or group

Question 38

Define the term nucleophile

Answer 38

A molecule or negatively charged ion with a lone pair of electrons that it can donate to a positively charged atome to form a covalent bond *Nucleophile means nucleus loving so attracted to the positive charge

Question 39

Describe a nucleophilic substition reaction

Answer 39

- The nucleophile attacks the electron deficient atom - The The nucleophile donates two electrons forming a dative covalent bond - The C-X bond breaks heteroyically- producing a X ion called the leaving group - Forming a carbocation - The nucleophile bonds with the carbocation