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Flashcards in Definitions Deck (129)
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1

Acid

A species that releases H+ ions in aqueous solution

2

Activation Energy

The minimum energy required to start a reaction by the breaking of bonds

3

actual yield

the amount of product obtained from a reaction

4

addition polymerisation

a formation of a very long molecular chain, by repeated addition of many unsaturated alkenes

5

addition reaction

a reaction in which a reactant is added to an unsaturated molecule to make a one saturated molecule

6

adsorption

the process that occurs when a gas or a liquid or solute is held to the surface of a solid

7

alicyclic

containing carbon atoms joined together in a ring that is not aromatic

8

aliphatic

containing carbon atoms joined together in branched (straight) or branched chains

9

alkali

a type of base that dissolves in water to release hydroxide ions

10

alkanes

the hydrocarbon homologous series with the general formula CnH2n+2

11

alkenes

the hydrocarbon homologous series with one double carbon-to-carbon bonds and the general formula CnH2n

12

alkyl group

a side chain formed by removing a hydrogen atom removed from and alkane parent chain. Amy alkyl group is often show as 'R'

13

alkynes

the hydrocarbon homologous series with one triple carbon-to-carbon bonds and the general formula CnH2n-2

14

amount of substance (n)

the quantity whose unit of the mole. chemists use amount of substance as a means of counting atoms

15

anhydrous

containing no water molecules

16

anion

a negatively charged ion with more electrons than protons

17

aromatic

containing one or more benzene rings

18

atom economy

(molar mass of products/total molar mass)*100%

19

atomic number (z)

the number of protons in the nucleus of an atom(proton number)

20

atomic orbital

a region around the nucleus that can hold up to two electrons, with opposite spins

21

average bond enthalpy

the average enthalpy change that takes place when breaking by homolytic fission one mole of a given type of bond in the molecules of a gaseous species

22

avogadro constant

6.022*10^23 mol^-1, the number of atoms per mole of carbon 12

23

avogadro's hypothesis

equal volumes of gases at the same temperature and pressure contain the same number of molecules

24

base

a compound that neutralises an acid to form a salt

25

binary compound

a compound containing two elements only

26

bond angle

the angle between two bonds at an atom

27

bonded pair

a pair of electrons shared between to make a covalent bond

28

carbocation

an ion that contains a positively charged carbon atom

29

catalyst

a substance that increases the rate of a chemical reaction without being used up in the process. A catalyst provides an alternative route for the reaction with a lower activation energy

30

cation

a positively charged ion with fewer electrons than protons

31

chain reaction

a reaction in which the propagation steps release new radicals that continue the reaction

32

cis-trans isomerism

a special type of E/Z isomerism in which there are two non hydrogen groups and two hydrogen atoms around the C-C double bond - the cis isomer (Z isomer) has hydrogen atoms on each carbon on the same side, whilst the trans isomer (E isomer) has hydrogen atoms on each carbon on different sides

33

closed system

a system isolated from its surroundings

34

collision theory

two reacting particles must collide for a reaction to occur and must be in the correct orientation and have sufficient energy to overcome the activation energy of the reaction

35

coordinate bond

a shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only. Also called a dative covalent bond.

36

covalent bonding

the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

37

dative covalent bond

a shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only; also called a coordinate bond

38

dehydration

an elimination reaction in which water is removed from a saturated molecule to make an unsaturated moelcule

39

delocalised electrons

electrons that are shared between more than two atoms

40

desorption

release of an absorbed substance from a surface

41

dipole

a separation in electrical charge so that one atom of a polar covalent bond, has a small positive charge delta+ and the other has a small negative charge delta-

42

dipole-dipole force

an attractive force between permanent dipoles in neighbouring polar moleculs

43

displacement reaction

a reaction in which a more reactive element displaces a less reactive element from an aqueous solution of its ions

44

displayed formula

a formula that shows the relative positioning of all atoms in a molecule and the bonds between them

45

disproportionation

a redox reaction in which an element is both oxidised and reduced

46

dynamic equilibrium

the equilibrium that exists in a closed system when the rate of teh forward reaction is equal to the rate of the reverse reaction and concentrations do not change

47

E/Z isomerism

a type of stereosiomerism in which different groups attached to each carbon of a C=C double bond may be arranged differently in space because of the restricted roatation of the C=C bond

48

electron configuration

a shorthand method for showing how electrons occupy sub-shells in an atom

49

elecgtronegativity

a measure of the attraction of a bonded atom for the pair of electrons in a covalent bond

50

electrophile

an atom or group of atoms that is attracted to an electron-rich centre, where it acceepts a pair of electrons

51

electrophilic addition

an adition reaction in which the first step is attack by an electrophile on a region of high electron density

52

elimination reaction

the removal of a molecule from a saturated molecule to make an unsaturated molecule

53

empirical formula

a formula that shows the simplest whole number ratio of atoms of each element present in a compound

54

end point

the point in a titration where the indicator changes colour; the end point indicates when the reaction is just complete

55

endothermic reaction

a reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surroundings (deltaH is positive)

56

enthalpy

the heat content that is stored in a chemical system

57

enthalpy charge (deltaH)

difference in enthalpy between reactants an products in a reaction

58

enthalpy cycle

a diagram showing alternative routes between reactants and products which allpws the indirec determination of an enthalpy change from other known enthalpy changes using hess' law

59

enthalpy profile diagram

a diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products

60

equilibrium constant

a measure of the position of equilibrium; the magnitude of an equilibrium constant indicates whether there are more reactants or more products in an equilibrium system.

61

exothermic reaction

a reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants resulting in heat loss to the surroundings (deltaH negative)

62

fingerprint region

an area of an infrared spectrum below 1500cm^-1 that gives a characteristic pattern for different compounds

63

first ionisation energy

the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions

64

fractional distillation

the separation of components in a liquid mixture by their different boiling points into fractions with different composition

65

fragment ions

ions formed from the breakdown of the molecular ion in a mass spectrometer

66

fragmentation

the process in mass spectrometry that cause a positive ion to split into smaller pieces, one of which is a positive fragment ion

67

functional group

the part of the organic molecule responsible for its chemical reaction

68

general formula

the simplest algebraic formula of a member of a homologous series. For example the general formula of alkanes is CnH2n+2

69

giant covalent lattice

a three dimensional structure of atoms, bonded together by strong covalent bonds

70

giant ionic lattice

a three dimensional structure of oppositely charged ions bonded together by strong ionic bonds

71

giant metallic lattice

a three dimensional structure of positive ions and delocalised electrons, bonded together by strong metallic bonds

72

group

a vertical column in the periodic table. elements in a group have similar chemical properties and their atoms have the same number of outer shell electrons

73

hess' law

in a reaction take place by more than one route and the initial and final conditions are the same, the total enthalpy change is the same for each route

74

heterogeneous catalysis

a reaction in which the catalyst has a different physical state from the reactants; frequently reactants are gases whilst the catalyst is solid

75

heterolytic fission

the breaking of a covalent bond with both of the bonded electrons going to each atom, forming a cation (positive ion) and an ion (negative ion)

76

homogeneous catalysis

a reaction in which the catalyst and reactants are in the same physical state, which is most frequently the aqueous or gaseous state

77

homologous series

a series of organic compounds with the same functional but with each successive member differing by CH2

78

homolytic fission

the breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radicals

79

hydrated

a crystalline compound containing water molecules

80

hydrocarbon

a compound containing carbon and hydrogen only

81

hydrogen bond

a strong dipole-dipole attraction between an electron-deficient hydrogen atom of -NH, -OH, or HF on one molecule and lone pair of electrons on a highly electronegative atom containing N, O or F on a different molecule

82

hydrolysis

a reaction with water that breaks a chemical compound into two compounds, the H and OH in a water molecule becomes incorporated into the two compounds

83

induced dipole-dipole interaction

attractive forces between induced dipoles in different molecules; also called london forces

84

initiation

the first stage in a radical reaction in which radical starts when a covalent bond is broken by homolytic fission of a covalent bond

85

intermediate

a species formed during a reaction that reacts further and is not present in the final products

86

intermolecular forces

an attractive force between molecules. Intermolecular forces can be london forces, permanent dipole-dipole interactions or hydrogen bonding

87

ion

a positively or negatively charged atom or a (covalently bonded) group of atoms (a polyatomic ion), where the number of electrons is different from the number of protons

88

ionic bonding

the electrostatic attraction between positive and negative ions

89

isotope

atoms of the same element with different numbers of neutrons and different masses

90

le chatelier's principle

when a system in dynamic equilibrium is subjected to a external change, the system readjusts itself to minimise the effect of the change and to restore equilibrium

91

limiting reagent

the reactant that is not in excess which will be used up first and stop the reaction

92

london forces

attractive forces between induced dipoles in different molecules; also known as induced dipole-dipole interactions

93

lone pair

an outer shell pair of electrons that is not involved in chemical bonding

94

mass number A

the sum of the number of protons and neutrons in the nucleus; also known as nucleon number

95

metallic bonding

the electrostatic attraction between positive metal ions and delocalised electrons

96

concentration

the amount of solute, in mole, dissolved in 1 dm^3 of solution

97

molar gas volume

the volume per mole of gas molecules at a stated temperature and pressure

98

molar mass

the mass per mole of a substance, in units of gmol^-1

99

mole

the amount of any substance containing many elementary particles as there are carbon atoms in exactly 12g of the carbon-12 isotope

100

molecular formula

a formula that shows the number and type of atoms of each element present in a molecule

101

molecular ion

the positive ion formed in mass spectrometry when a molecule loses an electron

102

molecule

the smallest part of a covalent compound that can exist while retaining its chemical identity consisting of two or more atoms covalently bonded together

103

monomer

a small molecule that combines with many other monomers to form a polymer

104

neutralisation

the reaction between an acid and a base to produce a salt

105

nomencalture

a system of naming compounds

106

non polar

with no charge seperation across a bond or in a molecule

107

nucleon number

the number of protons and neutrons in an atom

108

nucleophile

an atom or group of atoms that is attracted to an electron- deficient carbon atom where it donates a pair of electrons to form a new covalent bond

109

nucleophilic substitution

a reaction in which a nucleophile is attracted to an electron deficient carbon atom and replaces an atom or group of atoms on it

110

oxidation

loss of electrons or an increase in oxidation number

111

oxidation number

a measure of the number of electrons that na atom uses to bond with atoms of another element. oxidation number are derived from a set of rules

112

oxidation state

the oxidation number

113

oxidising agent

a reagent that oxidises another species

114

pi bond

a bond formed by the sideways overlap of two p orbitals, containing two electrons and with the electron density concentrated above and below the line joining the nuclei of the bonding atoms

115

partial dissociation

the splitting of some of a species in solution into aqueous ions

116

pauling electronegativity value

a value assigned as a a measure of the relative attraction of a bonded atom for the pair of electrons in a covalent bond

117

percentage yield

actual yield of a product/theoretical yield of a product *100%

118

periodicity

a repeating trend in properties of the elements across each period of the periodic table

119

period

a horizontal row of elements in the periodic table. elements show trend in properties across a period

120

permanent dipole

a small charge difference that does not change across a bond, with positive and negative partial changes on the bonded atoms: the result of the bonded atoms having different electronegatives

121

permanent dipole-dipole interactions

attractive forces between the permanent dipoles in different molecules

122

polar molecule

a molecule with an overall dipole, having taken into account any dipoles across bonds and the shape of the molecule

123

polar covalent bond

a bond with a permanent dipole, having positive and negative partial changes on the bonded atoms

124

polyatomic ion

an ion containing more than one atom

125

polymer

an large molecule formed from many thousands of repeat units of smaller molecules known as monomers

126

position of equilibrium

the relative quantities of reactants and products, indicating the extent of a reversible reaction at equilibrium

127

primary

on a carbon atom at the end of a chain

128

priamry alcohol

an alcohol in which the -OH. group is attached to a carbon atom that is attached to two or three hydrogen atoms

129

principal quantum number

a number representing the relative overall energy of each orbital, which increases with distance from the nucleus. the sets of orbitals with the same n-value are referred to as electron shells or energy levels