OCR-A A-level Chemistry

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relative isotopic mass

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Definitions & Key Facts

183 Terms

1

relative isotopic mass

mass of an atom of an isotope compared to 1/12 the mass of an atom of carbon-12

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relative atomic mass

average mass of the atoms of an element taking account of all of the isotopes compared to 1/12 the mass of an atom of carbon-12

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3

relative molecular mass

average mass of a molecule compared to 1/12 the mass of an atom of carbon-12

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4

isotopes

atoms of the same element with the same number of protons but different numbers of neutrons

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5

spectator ions

species which are not changing physical state or oxidation state... not in an ionic equation

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6

mole

amount of substance in grams which contains the same number of particles as there are atoms in 12g of carbon-12

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7

empirical formula

simplest whole number ratio of atoms of each element in a compound

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8

general formula

algebraic formula for a homologous series

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9

molecular formula

actual number of atoms of each element in a molecule

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10

structural formula

minimum detail required to understand the structure of a molecule

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11

displayed formula

shows all the covalent bonds in a molecule

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12

skeletal formula

shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups

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13

% yield

(actual yield/theoretical yield) x 100

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14

% atom economy

mass of desired product / total mass of reactants x 100

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15

Bronsted-Lowry acid

proton donor

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16

Bronsted-Lowry base

proton acceptor

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17

alkali

soluble base which releases OH⁻ ions in solution

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18

salt

ionic compound that forms when H⁺ ion in an acid is replaced by a metal ion or the ammonium ion

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19

strong acid

acid which completely dissociates in aqueous solution

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20

weak acid

acid which partially dissociates in aqueous solution

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21

% uncertainty

(uncertainty/measurement) x 100 x number of measurements

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22

oxidation

addition of oxygen loss of hydrogen loss of electrons increase in oxidation state

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23

reduction

loss of oxygen gain of hydrogen gain of electrons decrease in oxidation state

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24

disproportionation

simultaneous oxidation and reduction of the same element

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25

oxidising agent

electron acceptor

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26

reducing agent

electron donor

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27

orbital

region of space which can be occupied by a maximum of 2 electrons with opposite spin

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28

ionic bond

electrostatic attraction between positive metal ions and negative non-metal ions

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29

metallic bond

electrostatic attraction between positive metal ions and delocalised electrons.

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30

covalent bond

electrostatic attraction between a pair of bonded nuclei and a bonding pair of electrons

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31

dative bond

electrostatic attraction between a pair of bonded nuclei and a bonding pair of electrons which originate from one of the bonded atoms

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32

BeCl₂

Be is in Grp2 2 outer electrons 2 bp repel equally get as far apart as possible

linear 180°

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33

BF₃

B is in Grp3 3 outer electrons 3 bp repel equally get as far apart as possible

trigonal planar 120°

<p>B is in Grp3 3 outer electrons 3 bp repel equally get as far apart as possible</p><p>trigonal planar 120°</p>
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34

CH₄

C is in Grp4 4 outer electrons 4 bp repel equally get as far apart as possible

tetrahedral 109.5°

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35

NH₃

N is in Grp5 5 outer electrons 3 bp and 1 lp lp : bp repulsion > bp : bp repulsion get as far apart as possible

trigonal pyramid 107°

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36

H₂O

O is in Grp6 6 outer electrons 2 bp and 2 lp lp : lp repulsion > lp : bp repulsion > bp : bp repulsion get as far apart as possible

V-shape / Bent / Non-linear 104.5°

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37

SF₆

S is in Grp6 6 outer electrons 6 bp repel equally get as far apart as possible

Octahedral 90° and 180°

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38

electronegativity

ability of an atom to attract electrons within a covalent bond

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39

London forces

induced dipole-dipole forces instantaneous dipole-induced dipole forces dispersion forces

random movement of the electron cloud causes an uneven charge distribution and sets up an instantaneous dipole in one molecule

this induces a dipole in a neighbouring molecule and leads to a temporary attraction

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40

permanent dipole-permanent dipole force

intermolecular force between permanent dipoles in neighbouring polar molecules

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41

hydrogen bond

strong intermolecular force between a δ⁺H atom covalently bonded to N, O or F on one molecule

and a lone pair of electrons on N, O or F of a neighbouring molecule

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42

periodicity

repeating pattern of chemical and physical properties across different periods

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43

first ionisation energy

energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of +1 gaseous ions

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44

second ionisation energy

energy required to remove 1 mole of electrons from 1 mole of +1 gaseous ions to form 1 mole of +2 gaseous ions

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45

exothermic

bond making process

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46

endothermic

bond breaking process

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47

activation energy

minimum amount of energy required to start a chemical reaction

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48

standard conditions (⦵)

298 K 100 kPa all solutions 1 moldm⁻³

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49

standard enthalpy change of formation △fH⦵

enthalpy change when...

1 mole of a compound is formed from its elements in their standard states

under standard conditions of 298K and 100kPa

with all reactants and products in their standard states

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50

standard enthalpy change of combustion △cH⦵

enthalpy change when...

1 mole of a substance completely combusts in excess oxygen

under standard conditions of 298K and 100kPa

with all reactants and products in their standard states

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51

standard enthalpy change of reaction △rH⦵

enthalpy change when...

the reaction occurs in the molar ratio specified by the balanced equation

under standard conditions of 298K and 100kPa

with all reactants and products in their standard states

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52

standard enthalpy change of neutralisation △neutH⦵

enthalpy change when...

1 mole of water is formed from a reaction between an acid & a base

under standard conditions of 298K and 100kPa

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53

Q

Q = mc△T

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54

△H

△H = ⁻Q/1000n

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55

mean bond enthalpy

energy required to break 1 mole of gaseous covalent bonds

averaged over a number of different molecules

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56

Hess' law

enthalpy change of a reaction is independent of the route taken

providing the initial and final conditions are the same

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57

catalyst

speeds up a reaction

regenerated doesn't appear in the overall equation provides an alternative reaction pathway with a lower activation energy

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58

heterogenious catalyst

catalyst in a different physical state to the reactants

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59

homogenious catalyst

catalyst in the same physical state as the reactants

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60

dynamic equilibrium

forward rate = back rate concentrations of all reactants and products are constant closed system

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61

Le Chatelier's principle

when the conditions of a system in equilibrium are changed

the position of equilibrium will shift to reduce the effect of the change

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62

saturated

single carbon-carbon bonds only

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63

unsaturated

compound with one or more double or triple carbon-carbon bonds

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64

aliphatic

compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings

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65

alicyclic

aliphatic compound arranged in non-aromatic rings with or without side chains

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66

aromatic

compound containing at least one benzene ring

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67

homologous series

series of organic compounds with the.. same functional group same general formula successive member differs by CH₂

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68

functional group

atom, group of atoms or region of a molecule responsible for its reactions and properties

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69

structural isomers

same molecular formula different structural formula

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70

stereoisomers

same molecular formula same structural formula different arrangement of atoms in space

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71

radical

species with an unpaired electron

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72

homolytic fission

covalent bond breaking process where each atom receives one of the bonding electrons

forms radicals

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73

heterolytic fission

covalent bond breaking process where one atom receives both of the bonding electrons

forms ions

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74

sigma bond

covalent bond formed by end-on overlap of orbitals

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75

pi bond

covalent bond formed by sideways overlap of p-orbitals

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76

3 types of stereoisomers

E-Z isomers

cis-trans isomers

optical isomers

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77

E-Z isomerism

type of stereoisomerism

restricted rotation about a C=C double bond

each C in the C=C double bond attached to 2 different atoms or groups

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78

cis-trans isomerism

type of stereoisomerism

restricted rotation about a C=C double bond

a particular atom or group is attached to each of the C atoms in the C=C double bond

like groups on opposite sides of the double bond - trans like groups on same side of the double bond - cis

also found in square planar and octahedral complexes

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79

optical isomerism

type of stereoisomerism

occurs when there is an asymmetric (chiral) carbon atom attached to 4 different atoms or groups resulting in non-superimposable mirror images (enantiomers)

occurs where there are two or three bidentate ligands in an octahedral complex

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80

nucleophile

electron pair donor

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81

electrophile

electron pair acceptor

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82

carbocation

positively charged organic species

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83

1° carbocation

positive C is bonded to 1 other C

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84

2° carbocation

positive C is bonded to 2 other Cs

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85

3° carbocation

positive C is bonded to 3 other Cs

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86

Markownikoff's rule

rule applied to determine the product mixture when...

an asymmetric alkene reacts with an asymmetric electrophile

major product is formed from the more stable 2° or 3° carbocation

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87

primary alcohol

C to which the OH is bonded, is bonded to 1 other C

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88

secondary alcohol

C to which the OH is bonded, is bonded to 2 other Cs

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89

tertiary alcohol

C to which the OH is bonded, is bonded to 3 other Cs

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90

hydrocarbon

compound that contains carbon and hydrogen only

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91

CFC

compound that contains chlorine, fluorine and carbon only

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92

HFC

compound that contains hydrogen, fluorine and carbon only

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93

fingerprint region

complicated region of an IR spectrum below 1500 cm⁻¹ caused by vibrations of the whole molecule compared to a spectral database for a positive ID

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94

molecular ion

molecule minus an electron

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95

fragmentation

process where a molecular ion breaks into a positive ion and a radical

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96

Alkane to Haloalkane

Halogen UV light

Rad Sub

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97

Alkene to Alkane

H2, Ni catalyst

Reduction

Heterogenious Catalysis

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98

Alkene to Polyalkene

High pressure and a catalyst

Addition Polymerisation

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99

Alkene to Dihaloalkane

X2 rtp

Elec Add

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100

Alkene to Haloalkane

HX rtp

Elec Add

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