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CHEM > Definitions > Flashcards

Definitions Flashcards

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1
Q

Atomic number

A

The number of protons in the nucleus, therefore the number of electrons in an atom

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2
Q

Isotope

A

Atoms with the same number of protons but different numbers of neutrons

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3
Q

Mass number

A

The total number of protons plus neutrons in the nucleus

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4
Q

Relative atomic mass

A

The average mass of one atom of an element taking into account the relative abundance of its naturally occurring isotopes, compared to the mass if one twelfth of an atom of carbon 12

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5
Q

Relative molecular mass

A

Average mass on one molecule or combined compared to one twelfth of an atom of carbon 12

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6
Q

Atom economy

A

The efficiency if a chemical reaction by comparing the total mass of atoms in the product with the total mass of atoms in the starting materials

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7
Q

Empirical formula

A

The simplest whole number ratio of aroma of each element present in a compound

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8
Q

Molecular formula

A

Represents the actual number of atoms of each element in one molecule of a compound

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9
Q

Percentage Yeild

A

The efficiency of a chemical reaction by comparing the actual yield to the theoretical yield

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10
Q

Relative formula mass

A

The average mass of each atom in the formula compared to one twelfth of an atom of carbon-12

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11
Q

Spectator ions

A

Ions that are unchanged during chemical reactions, they take no part in a reaction

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12
Q

Delocalised

A

Describes electrons that are spread over several atoms to help bond them together

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13
Q

Dipole-dipole force

A

An intermolecular force that results from the attraction between molecules with permanent dipoles

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14
Q

Electronegativity

A

The power of an atom to attract the electron density in a covalent bond towards itself

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15
Q

Hydrogen bonding

A

A type of intermolecular force in which a hydrogen atom interacts with a more electronegative atom with a delta negative charge either nitrogen oxygen or fluorine

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16
Q

Van der Waals force

A

A type of intermolecular force of attraction that is caused by instantaneous dipoles and acts between all atoms and molecules

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17
Q

Bond dissociation enthalpy

A

The enthalpy change required to break a covalent bond with all species in the gaseous stare

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18
Q

Endothermic

A

Describes a reaction in which heat is taken in as the reactants change to products; the temperature drops

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19
Q

Enthalpy change

A

A measure of heat energy given out or taken in when a chemical or physical change occurs

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20
Q

Enthalpy change of combustion

A

The enthalpy change when one mole of substance is completely burnt in oxygen under standard conditions all reactants and products in their standard States

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21
Q

Enthalpy change of formation

A

The enthalpy change when one mole of a substance is formed from its constituent elements under standard conditions, all reactants and products in their standard states

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22
Q

Exothermic

A

Describes a reaction in which heat is given out as the reactions change to products; the temperature rises

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23
Q

Hess’ law

A

The enthalpy change for a chemical reaction is independent of the route taken

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24
Q

Mean bond enthalpy

A

The average value of bond dissociation enthalpy doe a given type of bond taken from a range of different compounds

25
Q

Specific heat capacity

A

The amount of heat needed to raise the temperature of 1g of a substance by 1 degree

26
Q

Activation energy

A

The minimum energy that a particle needs in order to react

27
Q

Maxwell Boltzmann distribution

A

The distribution of energies do the molecules in a gas or liquid

28
Q

Catalyst

A

Substances that affect the rate of a chemical reaction without being chemically changed themselves or used up

29
Q

Closed system

A

One where react acts and products can’t escape

30
Q

Dynamic equilibrium

A

A situation in which the composition of a constant concern train reaction mixture does not change because both forward no backward reactions are proceeding at the same rate continuously

31
Q

Equilibrium mixture

A

Mixture of reactants and products formed when a reversible reaction is allowed to proceed in a closed container until no further change occurs

32
Q

Le Châtelier’s principle

A

If a system at equilibrium is disturbed the equilibrium moved in the direction that tends to reduce the disturbance

33
Q

Oxidation

A

A reaction in which an atom or group of atoms loses electrons

34
Q

Oxidising agent

A

A reagent that oxidises (removed electrons from) another species

35
Q

Reduction

A

A reaction is which an atom or group of atoms gain electrons

36
Q

Reducing agent

A

A reagent that reduces (adds elections to) another species

37
Q

Redox reaction

A

A reaction in which elections are transferred from one species to another

38
Q

Displacement reaction

A

A chemical reaction in which one atom or group of atoms replaces another in a compound

39
Q

Disproportionation

A

Describes a redox reaction in which the oxidation number of some atoms of a particular element increases and that of other atoms of the same element decreases

40
Q

Functional group

A

An atom or group of atoms in an organic molecule which is responsible for the characteristic reactions of that molecule

41
Q

Homologous series

A

A set if organic compounds with the same functional group. The compounds differed in the length of their hydrocarbon chains, adding a CH2 each time, they have the same chemical properties and a trend in physical properties

42
Q

Isomer

A

Molecules that have the same molecular formula but whose atoms are arranged differently

43
Q

Stereoisomerism

A

Where two or more co lines have the same structural formula but differ in the arrangement of atoms in space

44
Q

Structural isomer

A

The same molecular formulae but different structural formulae

45
Q

Alkane

A

A hydrocarbon with C-C bonds and C-H bonds only. General formula CnH2n+2

46
Q

Fraction

A

A mixture of hydrocarbon collected over a particular range of boiling points during the fractional distillation of crude oil

47
Q

Free radical

A

A chemical species with an unpaired electron, usually highly reactive

48
Q

Incomplete combustion

A

A combustion reaction in which there is insufficient oxygen for all the carbon in the fuel to burn to carbon dioxide

49
Q

Saturated hydrocarbon

A

A compound containing only hydrogen and carbon bonds C-C and C-H single bonds

50
Q

Elimination

A

A reaction in which an atom or group if atoms is removed from a reactant

51
Q

Nucleophile

A

An ion or group of atoms with a negative charge or partially negatively charged area with a lone pair of electrons that takes part in an organic reaction by attacking a electron - deficient area in another reactant

52
Q

Addition polymers

A

They are made from a monomer or monomers with a carbon-carbon double bond

53
Q

Carbocation

A

An organic ion in which one if the carbon atoms has a positive charge

54
Q

Electrophile

A

An electron deficient atom, ion or molecule that takes part in an organic reaction by attacking areas of high electron density in another reactant

55
Q

Monomer

A

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

56
Q

Positive inductive effect

A

The tendency if some atoms or groups of atoms to release electrons via a covalent bond

57
Q

Carbon-neutral

A

A process in which as much carbon dioxide is absorbed from the atmosphere as is given out

58
Q

Fingerprint reigon

A

The area of an infra-red spectrum below about 1500cm-1. It is caused by complex vibrations of the whole molecule and shows the characteristics of a particular molecule

59
Q

Molecular ion

A

In mass spec, this is a molecule of the sample which has been ionised but which has not broken up during its flight through in instrument

CHEM (6 decks)

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