Ozone Flashcards
Calculating % composition- ppm
- Divide no. of molecules by 1,000,000
- Multiply answer by 100
Calculating conc. in ppm
Multiply % by 10,000
Equation for wave theory
speed of light c (ms-1) =wavelength (m) x frequency v (s-1)
Equation for particle model
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
What happens when radiation interacts with matter?
- The electromagnatic radiation transfers energy to the chemicals involved. This causes changes in the chemical depending on the chemical and amount of energy
Name the different types of energy association behaviors
- Translation (molecule moves around as a whole)
- Rotation (whole molecule)
- Vibration of bonds
- Electron energy
The order of increasing energy of the different energy behaviors
translational energy < rotational energy < vibrational energy < electronic energy
Why do the have different energy changes?
Its because different energy changes correspond to different parts of the spectrum
What electronic changes occur when a molecule absorbs UV radiation?
Excitation:
- Ionisation (lose of electrons)
- Dissociation (photodissociation- radicals formed)
- Release of energy
What are radicals?
Molecules or atoms with at least one unpaired electron- no overall charge
What is Bond fission?
Bond breaking and involves the redistribution of the electrons
What are the two types of bond fission?
Homolytic & heterolytic fission
What is heterolytic fission?
Both shared electrons go to just one of the atoms. Common when a bond is polar
What is homolytic fission?
One of the shared electrons goes to each atom. Produces radicals - non polar bonds
Ozone production
Reaction 1: O2 + hv = O + O
Reaction 2: O + O2 = O3
Reaction 3: O + O3 = O2 + O2
What is the Initiation, propagation & termination reaction?
Initiation - Radicals are formed
Propagation- Radicals as reactants and products
Termination - Two radicals collide and remove the radicals
Equation for rate of reaction
rate of reaction = change in property / time taken
Different ways of measuring the rate of reaction
- Measuring vol. of gas
- Measuring mass change
- pH measurement
- Colorimetry - chnage in colour
- Chemical analsyis
Describe the Chemical analysis process
Involves taking samples of reaction mixture at regular intervals and stopping the reaction before analysis.
The rest can be determined by titration
What affects the rate of a reaction?
- Conc. of the reaction / pressure
- Temperature
- Intensity of radiation
- Particle size / surface area
- Catalyst
Define activation enthalpy
The minimum kinetic energy required by a pair of colliding particles before a reaction will occur.
What is the Maxwell-Boltzmann distribution?
Defines the distribution of kinetic energies in a gas at a given temperature.
Define homogeneous catalyst
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.
Catalysts and equilibrium
Catalysts don’t affect the position of equilibrium, they only ALTER the RATE at which the equilibrium is attained not the COMPOSITION.
How do Chlorine and bromine atoms deplete ozone?
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.
Name the other radicals that also remove ozone
- Hydroxyl radical & nitrogen monoxide
* NO & NO2 are both radicals but not highly reactive -relatively stable
Define polar bonds
Atoms attracting bonding electrons unequally - difference in electronegativity
Define electronegativity
Electronegativity is a measure of the ability of an atom in a molecule to attract electrons in a chemical bond to itself
Increase in electronegativity along periods & groups
Groups: 1 < 2 < 3 < 4 < 5 < 6 < 7 Periods: 5 < 4 < 3 <2 < 1 * The closer to fluorine the more electronegative.
Define inter molecular bonds
Cause molecules to be attracted to each other- strength of bonds indicates the boiling point.
Define dipole
A molecule with both a positive & negative end.
* Molecular dipoles depend on electronegativity differences and shape of molecule (symmetry
Cause of permanent dipole
Occur when two atoms in a bond have substantially different electronegativities.
Cause of Instantaneous dipole
When electrons within a molecule are in constant motion
Cause of Induced dipole
Unpolarised molecule is next to a dipole, the dipole attracts or repels electrons in the unpolarised moecule inducing it.
Name the three types of intermolecular bonds
- 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
Hydrogen bonding
Strongest type of intermolecular bond- permanent-permanent dipole
Define substitution reaction
A reaction in which one atome or group in a molecule is replaced by another atom or group
Define the term nucleophile
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
Describe a nucleophilic substition reaction
- 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
