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AS Chemistry > Definitions > Flashcards

Definitions Flashcards

1
Q

Acid

A

A species that releases H+ ions in aqueous solution

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2
Q

Activation Energy

A

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

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3
Q

Actual Yield

A

The amount of product obtained from a reaction

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4
Q

Addition Polymerisation

A

The formation of a very long molecular chain (addition polymer), by repeated addition reactions of many unsaturated alkene molecules (monomers)

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5
Q

Addition Reaction

A

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

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6
Q

Adsorption

A

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

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7
Q

Alicyclic

A

Containing carbon atoms that are joined together in a ring that is not aromatic

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8
Q

Aliphatic

A

Any hydrocarbon that doesn’t contain a benzene ring (that isn’t aromatic)

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9
Q

Alkali

A

A type of base that dissolves in water to release hydroxide ions (OH-) (aq)

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10
Q

Alkanes

A

The hydrocarbon homologous series with the general formula CnH2N+2

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11
Q

Alkenes

A

The hydrocarbon homologous series with the general formula CnH2n

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12
Q

Alkyl Group

A

A side chain formed by removing a hydrogen atom removed from from an alkane parent chain. Any alkyl group is often shown as ‘R’

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13
Q

Alkynes

A

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

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14
Q

Amount of Substance, n

A

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

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15
Q

Anhydrous

A

Containing no water molecules

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16
Q

Anion

A

A negatively charged ion with more electrons than protons

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17
Q

Aromatic

A

Containing one or more benzene rings

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18
Q

Atom Economy

A

(Sum of Mr of desired products/Sum of Mr of all products)X100%

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19
Q

Atomic number, Z

A

The number of protons in the nucleus of an atom

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20
Q

Atomic orbital

A

A region around the nucleus that can hold a maximum of 2 electrons, with opposite spins

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21
Q

Average Bond Enthalpy

A

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

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22
Q

Avogadro Constant

A

6.02X10-23mol-1, the number of atoms in one mole of carbon-12

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23
Q

Avogadro’s Hypothesis

A

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

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24
Q

Base

A

A compound that neutralises acids to form a salt

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25
Q

Binary compound

A

A compound containing two elements only

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26
Q

Bond Angle

A

The angle between two bonds of an atom

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27
Q

Bonded Pair

A

A pair of electrons shared between two atoms to form a covalent bond

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28
Q

Carbocation

A

An ion that contains a positively charged carbon atom

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29
Q

Catalyst

A

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

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30
Q

Cation

A

A positively charged ion with fewer electrons than protons

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31
Q

Chain Reaction

A

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

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32
Q

cis-trans Isomerism

A

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) has hydrogen atoms on each carbon on the same side whilst the trans (E) isomer has hydrogen atoms on each carbon on different sides

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33
Q

Closed System

A

A system isolated from its surroundings

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34
Q

Collision Theory

A

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

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35
Q

Coordinate Bond (Dative Covalent Bond)

A

A shared pair of bonded electrons which have been provided by one of the bonding atoms only

36
Q

Covalent Bonding

A

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

37
Q

Dehydration

A

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

38
Q

Delocalised electrons

A

Electrons that are shared between more than 2 atoms

39
Q

Desorption

A

Release of an adsorbed substance from a surface

40
Q

Dipole

A

A seperation in electrical charge so that one atom of a polar covalent bond, or one end of a polar molecule, has a small positive partial charge and the other has a small negative charge

41
Q

Dipol-Dipole force

A

An attractive force between permanent dipoles in neighbouring polar molecules

42
Q

Displacement reaction

A

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

43
Q

Displayed formula

A

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

44
Q

Disproportionation

A

A redox reaction in which the same element is simultaneously oxidised and reduced

45
Q

Dynamic Equilibrium

A

The equilibrium that exists in a closed system when the rate of the forward reaction is the same as the rate of the reverse reaction and concentrations do not change

46
Q

E/Z Isomerism

A

A type of stereoisomerism in which different groups attached to each carbon of a C=C double bond may be arranged differently in space due to the lack of free rotation of the C=C bond

47
Q

Electron configuration

A

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

48
Q

Electronegativity

A

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

49
Q

Electrophile

A

An atom or group of atoms that are attracted to an electron-rich centre where they accept a pair of electrons

50
Q

Electrophilic Addition

A

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

51
Q

Elimination Reaction

A

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

52
Q

Empirical Formula

A

A formula that shows the simplest whole-number ratio or atoms of each element present in the compound

53
Q

End Point

A

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

54
Q

Endothermic Reaction

A

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)

55
Q

Enthalpy

A

The heat content that is stored in a chemical system

56
Q

Enthalpy change delta H

A

Difference in enthalpy between reactants and products in a reaction

57
Q

Enthalpy cycle

A

A diagram showing alternative routes between reactants and products which allows the indirect determination of an enthalpy change from other known enthalpy changes using Hess’ Law

58
Q

Enthalpy profile diagram

A

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

59
Q

Equilibrium constant, K

A

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

60
Q

Exothermic reaction

A

A reaction in which the enthalpy of the products is less than the enthalpy of the reactants, resulting in heat loss to the surroundings (deltaH is negative)

61
Q

Fingerprint region

A

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

62
Q

First Ionisation Energy

A

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

63
Q

Fractional Distillation

A

The separation of components in a liquid mixture by their different boiling points into fractions with different compositions

64
Q

Fragment ions

A

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

65
Q

Fragmentation

A

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

66
Q

Functional group

A

The part of the organic molecule that is responsible for its chemical reactions

67
Q

General formula

A

The simplest algebraic formula of a member of a homologous series

68
Q

Giant covalent lattice

A

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

69
Q

Giant ionic lattice

A

A three-dimensional structure of atoms, bonded together by strong ionic bonds

70
Q

Giant metallic lattice

A

A three-dimensional structure of atoms, bonded together by strong metallic bonds

71
Q

Group

A

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

72
Q

Hess’ Law

A

If a reaction can take place by more than one route and the start and finish conditions are the same then the total enthalpy change for each route will be the same

73
Q

Heterogenous Catalysis

A

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

74
Q

Heterolytic Fission

A

The breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation and an anion

75
Q

Homogenous catalysis

A

A reaction in which the catalysis has the same physical state as the reactants, which is most frequently the aqueous or gaseous state

76
Q

Homologous series

A

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

77
Q

Homolytic Fission

A

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

78
Q

Hydrated

A

A crystalline compound containing water molecules

79
Q

Hydrocarbon

A

A compound containing carbon and hydrogen only

80
Q

Hydrogen Bond

A

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

81
Q

Hydrolysis

A

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

82
Q

Induced dipole-dipole interaction (London Forces)

A

Attractive forces between induced dipoles in different molecules

83
Q

Initiation

A

The first stage in radical substitution in which radicals start when a covalent bond is broken by Homolytic fission

84
Q

Intermediate

A

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

85
Q

Intermolecular Forces

A

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

86
Q

Ion

A

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

87
Q

Ionic bonding

A

The electrostatic attraction between positive and negative ions

AS Chemistry (2 decks)

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