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Z A Level Chemistry > Definitions > Flashcards

Definitions Flashcards

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1
Q

acid

A

A species that releases H+ ions in aqueous solution

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2
Q

acid dissociation constant

A

The equilibrium constant that shows the extent of dissociation of a weak acid
For a weak acid HA (Aq), Ka= [H+(aq)][A-(aq)]/[HA(aq)]

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3
Q

acid-base pair

A

A pair of two species that transform into each other by gain or loss of a proton

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4
Q

activation energy

A

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

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5
Q

actual yield

A

The amount of product obtained from a reaction

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6
Q

addition polymerisation

A

Formation of a very long molecular chain by repeated addition reactions of many unsaturated alkene molecules (monomers)

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7
Q

addition reaction

A

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

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8
Q

adsorption

A

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

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9
Q

alicyclic

A

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

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10
Q

aliphatic

A

Containing carbon atoms joined together in straight or branched chains

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11
Q

alkali

A

A type of base that dissolves in water forming hydroxide ions, OH-(aq) ions

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12
Q

alkanes

A

The hydrocarbon homologous series with single carbon-to carbon bond and the general formula CnH2n+2

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13
Q

alkenes

A

The hydrocarbon homologous series with at one double carbon-to-carbon bond and the general formula CnH2n

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14
Q

alkyl group

A

A side chain formed by removing a hydrogen atom removed from an alkane parent chain for example CH3, C2H5; any alkyl group is often shown as R

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15
Q

alkynes

A

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

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16
Q

amount of a substance

A

The quantity whose unit of the model, used as a means of counting any species such as atoms, ions and molecules

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17
Q

anhydrous

A

Containing no water molecules

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18
Q

anion

A

Negatively charged ion with more electrons than protons

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19
Q

aromatic

A

Containing one or more benzene rings

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20
Q

atom economy

A

(Sum of molar masses of desired products)/ (sum of molar masses of all products)

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21
Q

atomic (proton) number

A

The number of protons in the nucleus of an atom

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22
Q

atomic orbital

A

A region around the nucleus that can hold up two electrons with opposite spots

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23
Q

average bond enthalpy

A

The average enthalpy change that takes place when breaking by homolytic fission 1 mol of a given type of bond in the molecule of a gaseous species

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24
Q

Avogadro constant Na

A

The number of atoms per mole of the carbon-12 isotope (6.02 x 10^-23 mol^-1)

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25
Q

base

A

A compound that neutralises an acid to form a salt

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26
Q

binary compound

A

A compound contains two elements only

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27
Q

bond angle

A

The angle between two bonds at an atom

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28
Q

bond dissociation enthalpy

A

The enthalpy change that takes place when breaking by homiletic fission 1 mol of s given bond in the molecules of a gaseous species

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29
Q

bonded pair

A

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

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30
Q

Brønsted-Lowry acid

A

A species that is a proton, H+ donor

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31
Q

Brønsted-Lowry base

A

A species that is a proton, H+ acceptor

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32
Q

buffer solution

A

A system that minimises pH changes on addition of small amounts of an acid or a base

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33
Q

carbocation

A

An ion that contains positively charged carbon atom

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34
Q

catalyst

A

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

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35
Q

cation

A

A positively charged ions with fewer electrons than protons

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36
Q

chain reaction

A

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

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37
Q

chemical shift (delta)

A

A scale, in ppm that compares the frequency of the reference TMS at delta=0ppm

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38
Q

chiral carbon

A

A carbon atom attached to four different atoms or groups of atoms

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39
Q

chromatogram

A

A visible record showing the result of separation of the components of a mixture by chromatography

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40
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 isomer) has H atoms on each carbon on the same side; the trans isomer (E isomer) has H atoms on each carbon on different sides

41
Q

closed system

A

A system isolated from its surroundings

42
Q

collision theory

A

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

43
Q

complex ion

A

A transition metal ion bonded to ligands by coordinate bonds (dative covalent bonds)

44
Q

concentration

A

The amount of solute, in moles, dissolved in 1dm^3 (1000cm^3) of solution

45
Q

condensation reaction

A

A reaction in which two small molecules react together to form a larger molecules

46
Q

conjugate acid

A

A species that releases a proton to form a conjugate base

47
Q

conjugate acid

A

A species that accepts a proton to form a conjugate acid

48
Q

coordinate bond

A

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

49
Q

coordination number

A

The total number of coordinate bonds formed between a central metal ions and ligands

50
Q

covalent bond

A

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

51
Q

dative covalent

A

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

52
Q

dehydration

A

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

53
Q

delocalised electrons

A

Electrons that are shared between more than two atoms

54
Q

desorption

A

Release of an adsorbed substance from a surface

55
Q

dipole

A

A separation in electrical charged so that one atom of a polar covalent bond, or one end of a polar molecule, has a small positive charge (delta+) and the other has a small negative charge (delta-)

56
Q

displacement reaction

A

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

57
Q

displayed formula

A

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

58
Q

disproportionation

A

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

59
Q

dynamic equilibrium

A

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

60
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 because of the restricted rotation fo the C=C bond

61
Q

electron configuration

A

A shorthand representation that shows how electrons occur sub shells in an atom

62
Q

electronegativity

A

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

63
Q

electrophile

A

An atom (or group of atoms) which is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond

64
Q

electrophilic addition

A

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

65
Q

electrophilic substitution

A

A type of substitution reaction in which an electrophile is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond

66
Q

elimination reaction

A

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

67
Q

empirical formula

A

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

68
Q

enantiomers

A

Stereoisomers that are non-superimposable mirror images of each other; also called optical isomers

69
Q

end point

A

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

70
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

71
Q

enthalpy, H

A

The heat content that is stored in a chemical system

72
Q

enthalpy change deltaH

A

The difference between the enthalpy of the products and the enthalpy of the reactants

73
Q

enthalpy cycle

A

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

74
Q

enthalpy profile diagram

A

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

75
Q

entropy

A

The used for the dispersal of energy and disorder within the chemicals making up the chemical system

76
Q

equilibrium constant

A

A measurement of the position of equilibrium; the magnitude of an equilibrium constant indicates whether there are more reacts or more products in an equilibrium system

77
Q

equivalence point

A

The point in a titration at which the volume of one solution has reacted exactly with the volume of the second solution

78
Q

esterification

A

A reaction in which a carboxylic acid reacts with an alcohol to form an ester and water

79
Q

exothermic reaction

A

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

80
Q

fingerprint region

A

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

81
Q

first electron affinity

A

The enthalpy change that takes place when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions

82
Q

first ionisation energy

A

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

83
Q

fractional distillation

A

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

84
Q

fragment ions

A

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

85
Q

fragmentation

A

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

86
Q

free energy change deltaG

A

The balance between enthalpy entropy and temperature for a process given by deltaG=deltaH-TdeltaS. A process is feasible when delta G < 0

87
Q

functional group

A

The part of the organic molecule responsible for its chemical reactions

88
Q

general formula

A

The simplest algebraic formula of a member of a homologous series e.g. the general formula of the alkanes is CnH2n+2

89
Q

giant covalent lattice

A

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

90
Q

giant ionic lattice

A

A three dimensional structure of oppositely changed ions, bonded together by strong ionic bonds

91
Q

giant metallic structure

A

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

92
Q

group

A

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

93
Q

half life

A

The time taken for the concentration of a reactant to decrease by half

94
Q

hess’s Law

A

If a reaction can 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

95
Q

heterogenous catalysts

A

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

96
Q

heterogenous equilibrium

A

An equilibrium in which the species making up the reactants and products have different physical states

97
Q

heterolytic fission

A

The breaking of a covalent bond forming a cation (positive ion) and an anion (negative ion)

98
Q

homogenous catalysts

A

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

Z A Level Chemistry (13 decks)

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