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Chemistry > 01 - Key definitions > Flashcards

01 - Key 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 off a weak acid.

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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 two reactants join together to form one product.

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8
Q

Adsorption

A

The process that occurs when a gas or liquid or solute is held 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- ions.

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12
Q

Alkanes

A

The hydrocarbon homologous series with single carbon-carbon bonds and the general formula CnH2n+2.

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13
Q

Alkenes

A

The hydrocarbon homologous series with at least one carbon=carbon double bond.

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14
Q

Alkyl group

A

A side chain formed by removing a hydrogen atom removed from an alkane parent chain.

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15
Q

Alkynes

A

The hydrocarbon homologous series with at least one triple carbon-to-carbon bond.

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16
Q

Amount of substance

A

The quantity whose unit of the mole, 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

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 number

A

Also known as proton number and shows 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 to two electrons.

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23
Q

Average Bond Enthalpy

A

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

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24
Q

Avogadro constant

A

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

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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 containing 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 homolytic fission 1mol of a 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

Bronsted-Lowry Acid

A

A species that is a proton, H+, donor.

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31
Q

Bronsted-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.

33
Q

Carbocation

A

An ion that contains a positively charged carbon atom.

34
Q

Catalyst

A

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

35
Q

Cation

A

A positively charged ion with fewer electrons than protons.

36
Q

Chain reaction

A

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

37
Q

Chemical Shift

A

A scale, in ppm, that compares the frequency of an NMR absorption with the frequency of the reference TMS at 0ppm.

38
Q

Chiral carbon

A

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

39
Q

Chromatogram

A

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

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 opposite/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 sufficient 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 of solution.

45
Q

Condensation Reaction

A

A reaction in which two small molecules react together to form a larger molecule with elimination of a small molecule such as water.

46
Q

Conjugate Acid

A

A species that releases a proton to form a conjugate base.

47
Q

Conjugate Base

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 ion 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 known as 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 electron

A

Electrons which are shared between more than two atoms.

54
Q

Desorption

A

Release of an absorbed substance from a surface.

55
Q

Dipole

A

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

56
Q

Displacement Reaction

A

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

57
Q

Displayed formula

A

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

58
Q

Disproportionation

A

A redox reaction in which the same element has been 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 concentrations do 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 of the C=C bond.

61
Q

Electron configuration

A

A shorthand representation that shows the arrangement of electrons in sub-shells of an atom.

62
Q

Electronegativity

A

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

63
Q

Electrophile

A

An atom (or a 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/form an unsaturated molecule.

67
Q

Empirical Formula

A

The smallest and simplest whole-number ratio of atoms of elements present in a compound.

68
Q

Enantiomers

A

Stereoisomers that are non-superimposablemirror images of each other; also called optical isomers.

69
Q

End Point

A

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

70
Q

Endothermic Reaction

A

A reaction in which the enthalpy of products is greater than the enthalpy of reactants, resulting in heat being taken in form the surroundings (delta H is +).

71
Q

Enthalpy (H)

A

The heat content that is stored in a chemical system.

72
Q

Enthalpy Change (delta H)

A

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

73
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’s Law.

74
Q

Enthalpy Profile Diagram

A

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

75
Q

Entropy

A

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

76
Q

Equilibrium constant

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.

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 smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings (delta H-).

Chemistry (18 decks)

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