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OCR Chemistry - Exams > Definitions > Flashcards

Definitions Flashcards

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1
Q

Isotope

A

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

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2
Q

Atomic Number

A

Number of protons in the nucleus

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3
Q

Mass Number

A

Number of protons and neutrons in the nucleus

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4
Q

Ion

A

A positively or negatively charged single atom or covalently bonded group of atoms

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5
Q

Relative Isotopic Mass

A

The mass of an atom of an isotope compared with one twelfth of the mass of carbon-12

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6
Q

Relative Atomic Mass

A

The weighted mean mass of an atom of an element compared to one twelfth of the mass of carbon-12

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7
Q

Avogadro’s Constant

A

The number of atoms per mole of the carbon-12 isotope

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8
Q

Mole

A

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

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9
Q

Relative Formula Mass

A

The weighted mean mass of the formula unit of a compound compared with one twelfth of an atom of carbon-12

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10
Q

Empirical Formula

A

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

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11
Q

Molecular Formula

A

The actual number of atoms of each element in a molecule

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12
Q

Molar Volume

A

The volume per mole of a gas

At rtp it is 24 dm^3/mol

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13
Q

Concentration of a solution

A

The amount of solute in mol, dissolved in 1dm^3 of solution

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14
Q

Stoichiometry

A

The molar relationship between the relative quantities of substances taking part in a reaction

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15
Q

% Yield

A

Actual Yield / Theoretical Yield

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16
Q

Atom Economy

A

Molar mass of desired products / Sum of molar masses of all products

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17
Q

Aufbau Principle

A

Electrons fill the sub levels in order of increasing energy

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18
Q

Hund’s Rule

A

Within a sub level, the orbitals are first occupied singly by unpaired electrons

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19
Q

Ionic Bonding

A

The electrostatic attraction between positive and negative ions

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20
Q

Covalent Bonding

A

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

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21
Q

Bond Length

A

The distance between the nuclei of two bonded atoms

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22
Q

Bond Angle

A

The angle between two covalent bonds

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23
Q

Electronegativity

A

The measure of its tendency to attract the electron pair(s) from a covalent bond

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24
Q

Permanent Dipole

A

A small charge difference that does not change across a bond, with partial charges on the bonded atoms

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25
Q

Hydrogen Bonding

A

A strong dipole-dipole attraction between a hydrogen atom bonded to O, N or F and a lone pair on O, N or F

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26
Q

First Ionisation Energy

A

The energy required to remove one mole of electrons from one mole of gaseous atoms

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27
Q

Oxidation Number

A

A measure of the number of electrons that an atom uses to bond with atoms of another element

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28
Q

Oxidation

A

Loss of electrons or an increase in oxidation number

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29
Q

Reduction

A

Gain of electrons or a decrease in oxidation number

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30
Q

Oxidising Agent

A

A reagent that oxidises another species

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31
Q

Reducing Agent

A

A reagent that reduces another species

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32
Q

Disproportionation

A

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

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33
Q

Law of the Conservation of Energy

A

Energy cannot be created or destroyed, just converted from one form to another

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34
Q

Enthalpy

A

The heat content that is stored in a chemical system

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35
Q

Enthalpy Change

A

The heat exchanged with the surroundings during a chemical reaction
The difference between the enthalpy of the products and the reactants

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36
Q

Exothermic

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

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37
Q

Endothermic

A

A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken out of the surroundings

38
Q

Standard State

A

The state an element or compound will exist in at standard temperature and pressure

39
Q

Standard Enthalpy Change of Combustion

A

The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, with all the reactants and products in their standard state

40
Q

Standard Enthalpy Change of Reaction

A

The enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions, with all reactants and products in their standard states

41
Q

Standard Enthalpy Change of Neutralisation

A

The enthalpy change that accompanies the reaction of an acid by a base to form one mole of H2O under standard conditions, with all the reactants and products in their standard states

42
Q

Average Bond Enthalpy

A

Energy required to break one mole of a specific type of bond in a gaseous molecule

43
Q

Hess’ Law

A

If a reaction can take place by more than one route and the initial and final concentrations are the same, the total energy is the same for each route

44
Q

Enthalpy Change of Formation

A

The enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states

45
Q

Reaction Rate

A

The change in concentration of a reactant or product in a given time

46
Q

Catalyst

A

A substance that increases the rate of a chemical reaction without being used up in the process

47
Q

Activation Energy

A

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

48
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

49
Q

Le Chatelier’s Principle

A

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

50
Q

Closed Systen

A

A system isolated from its surroundings

51
Q

Equilibrium Constant

A

A measure of the position of equilibrium

52
Q

Homogeneous

A

In the same phase

53
Q

Heterogeneous

A

Different phases

54
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

55
Q

Half Life

A

The time taken for the concentration of the reactant to be reduced by half

56
Q

Reaction Mechanism

A

A series of steps that together make up the overall reaction

57
Q

Rate Determining Step

A

The slowest step in the reaction mechanism of a multi step reaction

58
Q

Mole Fraction

A

Number of mole of species / total number of moles of all species

59
Q

Partial Pressure

A

Mole fraction x total pressure

60
Q

Lattice Enthalpy

A

The change in enthalpy that accompanies the formation of one mole of ionic compound from its gaseous ions under standard conditions

61
Q

Standard Enthalpy Change of Atomisation

A

The change in enthalpy that accompanies the formation of one mole of gaseous atoms from the element in the standard state

62
Q

First Electron Affinity

A

The change in enthalpy that accompanies the formation of one mole of gaseous 1- ions from gaseous atoms

63
Q

Standard Enthalpy Change of Solution

A

The enthalpy change that takes place when one mole of a compound is completely dissolved in water under standard conditions

64
Q

Standard Enthalpy Change of Hydration

A

The enthalpy change that takes place when one mole of isolated gaseous ions is dissolved in water forming one mole of aqeuous ions under standard conditions

65
Q

Standard Entropy

A

The quantitative measure of the degree of disorder in a system

66
Q

Standard Entropy Change of Reaction

A

The entropy change that accompanies a reaction in the molar quantities expressed in the chemical equation under standard conditions, all reactants and products being in their standard states

67
Q

Free Energy Change

A

The balance between enthalpy, entropy and temperature for a process

68
Q

Redox

A

A reaction in which both reduction and oxidation take place

69
Q

Standard Electrode Potential

A

The emf of a half cell compared with a standard hydrogen half cell, measured at 298K with solution concentrations of 1 mol/dm^3 and a gas pressure of 1 atm

70
Q

Brønsted-Lowry Acid

A

It accepts a proton

71
Q

Brønsted-Lowry Base

A

It donates a proton

72
Q

Conjugate Acid

A

Brønsted-Lowry base that accepted a proton

73
Q

Conjugate Base

A

Brønsted-Lowry acid that donated a proton

74
Q

Acid Dissociation Constant

A

The equilibrium constant that shows the extended of dissociation of a weak acid

75
Q

pH

A

-log(10)[H+]

76
Q

Weak Acid

A

Partial dissociation of hydrogen atoms

77
Q

Strong Acid

A

Complete dissociation of hydrogen atoms

78
Q

Ionic product of water

A

Kw = [H+][OH-]

79
Q

Buffer Solution

A

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

80
Q

Transition Metal

A

A d-block element that forms an ion with an incomplete d sub-shell

81
Q

Complex Ion

A

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

82
Q

Coordination Number

A

The number of coordinate bonds attached to the central metal ion

83
Q

Ligand

A

A molecule or ion that can donate a pair of electrons to the transition metal ion to form a coordinate bond

84
Q

Denticity

A

The number of separate sites in a molecule or ion that can donate an electron pair to a transition metal ion

85
Q

Monodentate

A

A ligand that can donate one electron pair to a transition metal ion

86
Q

Bidentate

A

A ligand that can donate two electron pairs to a transition metal ion

87
Q

Tridentate

A

A ligand that can donate three electron pairs to a transition metal ion

88
Q

Stereoisomerism

A

Species with the same structural formula but with a different arrangement in space

89
Q

Optical Isomers / Enantiomers

A

Non-super imposable mirror images of each other

90
Q

Ligand Substitution

A

A reaction in which one or more ligands in a complex ion are replaced by different ligands

OCR Chemistry - Exams (7 decks)

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