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OCR A-Level Chemistry Salters B > The Ozone Story > Flashcards

Flashcards in The Ozone Story Deck (22)
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1

Converting from ppm to percentage

Divide by 1,000,000 and multiple by 100

2

Energy of a photon = ?

Planck constant x Frequency

3

What three things can happen when a molecule absorbs radiation

-Electrons can be excited to a higher energy state
-Photodissociation may occur and radicals are formed
-The molecules are ionised

4

Heterolytic and homolytic fission

Heterolytic fission - both electrons go to the same atom in the bond

Homolytic fission - both atoms in the bond get one electron, this causes the formation of radicals

5

Reactions for the breakdown of ozone

O + O2 --> O3
O + O --> O2
O + O3 --> O2 + O2

When added together:
O3 --> O2 + O

6

The stages of a radical chain reaction

Initiation - the stage which creates the radicals, only radicals on the right

Propagation - the middles stages, radicals on both sides of the reactions

Termination - the final reaction, only radicals on the left

7

Activation enthalpy

The minimum enery required by a pair of colliding particles before a reaction will occur

8

Chlorine as a ozone depletion catalyst

Cl + O3 --> ClO + O2
ClO + O --> Cl + O2
------‐------‐---
O3 + O --> O2 + O2

9

Hydroxyl radicals as a a ozone depletion catalyst

HO + O3 --> HO2 + O2
HO2 + O --> HO + O2
------‐------‐---
O3 + O --> HO + O2

10

Nitrogen monoxide as a ozone depletion catalyst

NO + O3 --> NO2 + O2
NO2 + O --> NO + O2
------‐------‐---
O3 + O --> O2 + O2

11

What is responsible for most of the properties and reactions of haloalkanes

The polar carbon-halogen bond, with the halogen being the negative side and the carbon being the positive side

12

Electronegativity

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

13

How does the size of the molecule affect the intermolecular forces

A larger molecule has stronger intermolecular forces and therefore a higher boiling point

Straight-chain alkanes have higher boiling points than their branched isomers as the straight-chain provides more contact between molecules and more opportunity for intermolecular bonds to form

14

What is a dipole and what are the types

A dipole is a molecule or part of a molecule with a positive end and a negative end, because of its polar bond

Permanent dipole-Permanent dipole
Permanent dipole-Induced dipole
Instantaneous dipole-Induced dipole

15

Permanent dipole-Permanent dipole

Strongest form of intermolecular bond, formed between two molecules with permanent dipoles

16

Permanent dipole-Induced dipole

The second strongest form of intermolecular bond. Occurs when a molecule with a permanent dipole induces a dipole in another molecule

17

Instantaneous dipole-Induced dipole

A temporary dipole occurs in one molecule which then induces a dipole in another molecule. This is the weakest form of intermolecular bond

18

Melting and boiling points of the halogens

Fluorine has the weakest intermolecular bonds as it is the smallest so melting and boiling points increase

19

Hydrogen bonding

The strongest form of intermolecular bond and is a special case of permanent dipole-permanent dipole

For hydrogen bonding to happen:
-A large dipole between a hydrogen atom and a highly electronegative atom
-A small hydrogen bonding which can get close to the electronegative atom
-A lone pair of electrons on the electronegative atom

20

Formation of radicals

A radicals are formed in the stratosphere when exposed to ultra violet light

21

Nucleophile

A molecule or negatively charged ion with a lone pair of electrons that it can donate to a positively charged atom to form a covalent bond

22

Which carbon-halogen bond will hydrolyse first and why

C-I bonds are most easily hydrolysed as they have the lowest bond enthalpy