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Definitions Flashcards

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1
Q

Atomic number

A

Number of protons in the nucleus of the atom

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2
Q

Mass number

A

The sum of the number of protons and neutrons in the nucleus of an atom

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3
Q

Nuclear charge

A

The total charge of all the protons in the nucleus and has the same value as the atomic number

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4
Q

Isotopes

A

Atoms of the same element with the same number of protons and electrons but a different number of neutrons in the nucleus

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5
Q

Relative atomic mass

A

Average mass of an atom relative to 1/12th of the mass of an atom of carbon 12

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6
Q

Relative isotopic mass

A

Average mass of an atom of an isotope relative to 1/12th of the mass of a carbon 12 atom

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7
Q

Relative molecular mass

A

The average mass of a molecule relative to 1/12 of the mass of an atom of carbon 12

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8
Q

Quantum shells

A

Electron shells, specify the energy level of an electron

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9
Q

First ionisation energy

A

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

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10
Q

Second ionisation energy

A

The energy required to remove 1 mole of electrons from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions

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11
Q

Orbital

A

A region in an atom that can hold up to two electrons with opposite spins

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12
Q

Periodicity

A

Trends in element properties with increasing atomic number

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13
Q

Hund’s rule

A

When electrons fill the orbital as they occupy them singularly before they pair up.

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14
Q

Pauli exclusion principle

A

Electrons with the same orbital must have opposite spins

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15
Q

Aufbau principle

A

As the atomic number increases, the electrons are added to the orbitals in order of increasing orbital energy until all electrons are accommodated

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16
Q

Shielding

A

A decrease in the nuclear charge experience by an outer electrons caused by electron electron repulsion between the outer shell electron and electrons from adjacent quantum shells

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17
Q

Ionic bond

A

Strong electrostatic forces of attraction between two oppositely charged ions. Strength of attraction depends on the relative sizes and charges of ions

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18
Q

Cation

A

A positively charged ion

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19
Q

Anion

A

A negatively charged ion

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20
Q

Isoelectronic species

A

Chemical species that have the same number of electrons.

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21
Q

Covalent bond

A

The strong electrostatic attraction between two nuclei and the shared pair of electrons between them.

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22
Q

Sigma bond

A

A bond that results from a direct overlap of two orbitals

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23
Q

Pi bond

A

A bond that is formed when two orbitals overlap sideways

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24
Q

Dative covalent bond

A

Occurs when one atom donates both electrons in a bond

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25
Q

Allotropes

A

Different forms of the same element. E.g. diamond graphite graphene

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26
Q

Malleable

A

A substance can be shaped

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27
Q

Ductile

A

A substance can be drawn into wires

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28
Q

Intermolecular forces

A

Forces between the molecules

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29
Q

Electronegativity

A

The ability of an atom to attract the bonding electrons in a covalent bond.

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30
Q

Dipole

A

The difference in charge between the two atoms of a covalent bond caused by a shift in the electron density in the bond due to the electronegativity different between the elements participating in bonding.

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31
Q

Metallic bonding

A

The electrostatic attraction between the metal ions and the sea of delocalised electrons that surround them

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32
Q

Delocalised electrons

A

The electrons that are not contained within an single atom or covalent bond

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33
Q

Bond length

A

Internuclear distance between two covalently bonded atoms

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34
Q

London forces

A

Weak intermolecular forces arising due to fluctuations of electron density within a non polar molecule. These fluctuations may temporarily cause an instantaneous dipole that can then induce a dipole in another molecule .

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35
Q

Permanent dipole-dipole interactions

A

Dipole-dipole attractions between polar molecules. Stronger than London forces

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36
Q

Hydrogen bond

A

An intermolecular force between a hydrogen bonded to a more electronegative atom ( N,O,F)

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37
Q

Oxidation number

A

The charge of an ion

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38
Q

Oxidation

A

Loss of electron, increase in oxidation number

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39
Q

Reduction

A

Gain in electrons, decrease in oxidation number

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40
Q

Redox

A

A reaction that involves oxidation and reduction

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41
Q

Oxidising agent

A

Accepts electrons and gets reduced in a redox reaction

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42
Q

Reducing agent

A

Donates electrons and gets oxidised in a redox reaction

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43
Q

Half equations

A

A full redox equation could be split into two half equations. Oxidation and reduction.

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44
Q

Disproportionation

A

A redox reaction involving an element in a single species being simultaneously oxidised and reduced .

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45
Q

Thermal stability

A

Refers to the extent to which a compound decomposes when subjected to heating

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46
Q

Electronic transition

A

The movement of electrons between energy levels. When an electron In a ground state absorbs some energy it can move to the excited state. When it moves back to ground state energy is released in a particular wavelength corresponding a specific colour.

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47
Q

Mole

A

The unit for amount of substance

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48
Q

Avogadro’s constant

A

The number of atoms in exactly 12g of carbon 12 6.02x10^23

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49
Q

Molar mass

A

Mass of one mole of the substance expressed in gmol-1

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50
Q

Empirical formula

A

The smallest whole number ration of atoms of each element in a compound

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51
Q

Molecular formula

A

The actual number of atoms of each element in a molecule

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52
Q

Spectator ions

A

Ions that do not take part in the reaction

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53
Q

Hydrate

A

A compound that has molecules of water of crystallisation

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54
Q

Solution

A

Standard solution is the one with accurately known concentration

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55
Q

Mass per concentration

A

Mass of solute per volume of solution

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56
Q

Molar concentration

A

Moles of solute per volume of solution

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57
Q

Primary standard

A

A substance used for preparation of a standard solution by weighing

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58
Q

Avogadros law

A

Provided conditions of temperature and pressure are the same, equal volume of gases contain the same number of molecules

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59
Q

Molar volume

A

The volume of 1 mole of a gas

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60
Q

Displacement reaction

A

More reactive element reacts to take the place of a less reaction element in a compound

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61
Q

Precipitation reaction

A

One take produces an insoluble solid

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62
Q

Error

A

A discrepancy between the value obtained in the experiment and an actual value

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63
Q

Precision

A

Refers to how close to each other the values obtained in an experiment are

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64
Q

Accuracy

A

Refers to how close these values are to the actual value

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65
Q

Concordant results

A

Results that lie close to each other

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66
Q

Margin error

A

The range in which the true value of a measurement could lie

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67
Q

Random errors

A

They occur when conditions are varied in an unpredictable manner

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68
Q

Systematic errors

A

Errors which are constant when you repeat an experiment, they are usually a result of the apparatus used.

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69
Q

Percentage uncertainty equation

A

(Uncertainty / reading)x100

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70
Q

Percentage yield

A

(Actual yield/theoretical yield) x100

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71
Q

Atom economy

A

Measure of the proportion of reaction atoms that become part of the desired product in the balanced chemical equation

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72
Q

Atom economy equation

A

(Molar mass of desired/molar mass of total ) x100

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73
Q

Hydrocarbon

A

A compound exclusively consisting of hydrogen and carbon atoms

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74
Q

Homologous series

A

Series of organic compounds with the same functional group and general formula

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75
Q

Functional group

A

A group of atoms responsible for the characteristic reactions of a particular compound

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76
Q

Addition

A

Joining two or more molecules together to form a larger molecule.

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77
Q

Polymerisation

A

Chemically combining lots of simple molecules to form a giant molecule

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78
Q

Repeating unit

A

A simplest pattern of the polymer that upon translation reproduces the whole structure

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79
Q

Elimination

A

When a small group of atoms breaks away from a larger molecule to form a c=c bond

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80
Q

Substitution

A

Whenone species is replaced by another

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81
Q

Hydrolysis

A

Breaking bonds in a molecule by a reaction with water

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82
Q

Dehydration

A

Reaction in which water is eliminated from a starting material

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83
Q

Saturated

A

Refers to a compound with all the c-c bonds being single bonds

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84
Q

Heterolytic fission

A

The process of breaking a covalent bond within a molecule leading to the formation of ions. Upon bond breaking one atom receives the electron pair and becomes negative it charged ion. Other atom becomes a cation

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85
Q

Homolytic fission

A

The process of breaking down a covalent bond within a molecule leading to the formation of radicals. Upon bond breaking one atom receives one electron from the bonding pair and both atoms become radicals

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86
Q

Radicals

A

A species with an unpaired electron. Represented in mechanisms by a single dot.

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87
Q

Free radical substitution

A

Photochemical reaction (requires UV light) between halogens and alkanes to form halogenoalkanes

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88
Q

Stereoisomerism

A

Occurs when two double bonded carbon atoms each have two different atoms of groups attached to them.

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89
Q

Structural isomerism

A

Occurs when species have the same molecular formula, but a different structural formula

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90
Q

Saturated hydrocarbons

A

Hydrocarbons which contain only single bonds between carbon atoms

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91
Q

Unsaturated hydrocarbons

A

Hydrocarbons which contain at least one carbon-carbon double bond

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92
Q

Cracking

A

Breaking long chain alkenes into smaller, more useful hydrocarbons. Helps to convert low demand hydrocarbons into more highly demanded ones

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93
Q

Reforming

A

Processing of straight chain hydrocarbons into branched chain alkanes and cyclic hydrocarbons for efficient combustion.

94
Q

Knocking

A

Alkanes explode of their own accord when the fuel/air mixture in an engine is compressed

95
Q

Complete combustion

A

Produces fully oxidised products as opposed to incomplete combustion

96
Q

Catalytic converters

A

Get rid of pollutants in cars by using platinum catalyst to convert them to harmless gases

97
Q

Biofuels

A

Fuels made from living matter over a short period of time

98
Q

Recycling

A

Conversion of waste from polymer into other useful materials

99
Q

Incinerator

A

A device for converting polymer waste into energy

100
Q

Feedstock

A

For conversion of polymer waste into compounds that can be used to synthesise new polymers

101
Q

Biodegradable

A

Refers to a polymer that can be decomposed by microbes. Usually has polar groups.

102
Q

Electrophile

A

Electrons pair acceptor in an organic mechanism. Attracted to areas with a lot of electrons

103
Q

Nucleophile

A

Electron pair donors in an organic mechanism. Attracted to electron-deficient areas.

104
Q

Electron releasing group

A

A group that releases the electron towards the atom it is joined to

105
Q

Carbocation

A

A carbon atom bearing a positive charge

106
Q

Markovnikoff’s rule

A

Weak statement - when adding a hydrogen hankies to an unsymmetrical alkene, the major product is formed from hydrogen adding to the carbon with more hydrogens, and hailed adding to the carbon with fewer hydrogens.

Strong statement - the major product of an electrophilic addition to the unsymmetrical alkene results from a reaction proceeding via most stable carbocationic intermediate.

107
Q

Distillation with addition

A

Performing the reaction under distillation conditions whilst adding one of the reagents. The product distills off as it forms in case of oxidation of an alcohol to an aldehyde.

108
Q

Solvent extraction

A

A method for separating a compound from a mixture by causing it to move to another solvent

109
Q

Fractional distillation

A

A distillation that utilises a fractionating column (packed glass beads that provide a surface for the vapour to condense and evaporate again) used to separate liquids of similar boiling points.

110
Q

Molecular ion peak

A

The peak with the highest m/z value. This is the molecular mass of the molecule being tested in the mass spectrometer

111
Q

[M+1] peak

A

The Peak which which occurs due to the isotope C13

112
Q

Fragmentation

A

When molecular ion is fragmented to smaller molecules / ions

113
Q

Infrared radiation

A

Has frequencies below that of red light

114
Q

Stretching

A

When a bond absorbs infrared radiation and therefore changes it’s length

115
Q

Transmittance

A

A value in the IR spectrum that shows the amount of radiation absorbed at a particular frequency

116
Q

IR spectroscopy

A

A technique used to determine the presence of certain functional groups within in the molecules

117
Q

Mass spectrometry

A

A technique that gives you information about the mass of a molecule and it’s fragments

118
Q

Enthalpy change

A

Heat energy change in a reaction at a constant pressure

119
Q

Standard conditions

A

100 kPa, 298K 1moldm-3

120
Q

Endothermic

A

Heat absorbed +ve Enthalpy change

121
Q

Exothermic

A

Heat given off -ve value of Enthalpy change

122
Q

Standard Enthalpy change of reaction

A

Enthalpy change when reaction occurs in the molar quantities shown in the chemical equation under standard conditions.

123
Q

Standard Enthalpy change of formation

A

Enthalpy change when 1 mole of a compound in formed from its elements in their standard states under standard conditions

124
Q

Standard Enthalpy of combustion

A

Enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions

125
Q

Standard Enthalpy of neutralisation

A

Enthalpy change when an acid and alkali react together under standard conditions to form 1 mole of water

126
Q

Equation for calorimeter calculations

A

Heat change mcAT
m is mass
c is heat capacity
AT is change in temperature

127
Q

Specific heat capacity

A

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

128
Q

Hess’s law

A

The total Enthalpy change is independent of the reaction pathway taken

129
Q

Bond Enthalpy

A

Amount of energy required to break 1 mole of the stated bond in the gas phase

130
Q

Enthalpy change of a reaction equation

A

Sum of bond enthalpies of reactant - sum of bond enthalpies of products

131
Q

Mean bond Enthalpy

A

Average amount of energy needed to break a specific type of bond, measured over a variety of different molecules

132
Q

Activation energy

A

The minimum amount of kinetic energy the particles need to react

133
Q

Catalyst

A

A substance that proves an alternative reaction route of lower activation energy and hence speeds up the reaction. It is chemically unchanged at the end of the process

134
Q

Heterogenous catalyst

A

Catalyst that is in a different phase from the reactants

135
Q

Homogenous catalyst

A

Catalyst in the same physical state as reactants.

136
Q

Maxwell-boltzmann distribution

A

A distribution of energy among the molecules of a gas in a closed system.
Area under the graph indicates the number of particles.

137
Q

Features of a dynamic equilibrium

A

Reversible reaction in a closed system
Forward and backward reactions occur simultaneously
Rate of forward reaction = rate of backwards reaction
There is no net change in concentrations of reactants and products

138
Q

Homogenous system

A

A system where all the chemicals are in the same phase

139
Q

Heterogenous system

A

A system where not all the chemicals are in the same phase

140
Q

Le chatelier’s principle

A

If there’s a small change in concentration, pressure/volume or temperature to a closed system in dynamic equilibrium, the equilibrium will shift to minimise the change.

141
Q

Contact process

A

A method of production. The key step involves the conversion of SO2 to SO3 in presence of oxygen, catalysed by V2O5.

142
Q

Mole fraction of gas

A

Number of moles of particular gas / total number of moles of all gases in the mixture

143
Q

Partial pressure

A

The pressure exerted by a particular gas in a mixture in a closed system. Relation to mole fraction: mole fraction x total pressure = partial pressure

144
Q

Total pressure

A

Sum of all partial pressures

145
Q

Reaction quotient vs Kc, Kp

A

The reaction quotient is the same as the equilibrium constant at equilibrium

146
Q

Brønsted-Lowry acid

A

A proton donor

147
Q

Brønsted-Lowry base

A

A proton acceptor

148
Q

Conjugate acid/base pair

A

Two species that differ by H+.
Acid loses hydrogen becomes base
Base gains hydrogen becomes acid

149
Q

pH

A

A figure expressing the acidity or alkalinity of a solution on a logarithmic scale.
7 is neutral
<7 is acidic
>7 alkali

150
Q

Equation to work out pH

A

pH = -log[H+]

151
Q

Ka

A

The acidic dissociation constant

152
Q

Equation for pKa

A

pKa = -log[Ka]
The lower the value the stronger the acid

153
Q

Kw

A

The ionic product of water

154
Q

Equation of pKw

A

pKw = -log[Kw]

155
Q

Lewis acid

A

Electron pair acceptor

156
Q

Lewis base

A

Electron pair donor

157
Q

Strong acid

A

Acid which completely dissociates in water

158
Q

Strong base

A

Base which completely dissociates in water

159
Q

Weak acid

A

Acid which dissociates only slightly in water

160
Q

Weak base

A

Base which is only slightly protonated in water

161
Q

Amphoteric

A

Refers to a substance that can act as an acid of base

162
Q

Monoprotic acid

A

Can release only one H+ upon dissociation

163
Q

Polyprotic acid

A

Can release more than one H+ upon dissociation

164
Q

Equivalence point

A

The point when full neutralisation occurs

165
Q

End point

A

The point during the titration when the indicator changes the colour.

166
Q

Buffer

A

A solution which resists change in pH when small amount of strong acid/base are added

167
Q

Acidic buffer

A

A buffer containing a weak acid and its conjugate base

168
Q

Alkaline buffer

A

A buffer containing a weak base and its conjugate acid

169
Q

Standard lattice energy

A

Energy change when 1 mole of an ionic solid is formed from its constituent gaseous ions under standard conditions

170
Q

Standard Enthalpy of atomisation

A

Enthalpy change when 1 mole of gaseous atoms is formed from the elements in its standard size. Always endothermic

171
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

172
Q

Enthalpy change of hydration

A

The Enthalpy change when one mole of a gaseous ion is completely dissolved in water under standard conditions

173
Q

Enthalpy change of solution

A

Enthalpy change when 1 mole of ionic solid completely dissolves in water under standard conditions to form an infinitely diluted solution

174
Q

Polarisation

A

Distortion of a charge distribute.

175
Q

Entropy

A

A measure of the disorder of a system.
A reaction that produces the greater number of molecules than the number of reactants molecules Will have a positive entropy change as there will exist more random arrangements of these molecules. I.e the system becomes more disordered.

176
Q

Gibbs free energy

A

A measure of feasibility of a chemical reaction.

177
Q

Anode

A

Positive electrode ( oxidation )

178
Q

Cathode

A

Negative electrode (reduction)

179
Q

Standard hydrogen electrode

A

A platinum foil immersed in 1 mol do -3 HCl enclosed in a tube containing hydrogen gas at standard pressure.

180
Q

Standard cell potential

A

Voltage measured under standard conditions when a half cell is connected to a standard hydrogen electrode. Tells you how readily a substance releases electrons relative to H2

181
Q

Salt bridge

A

A porous substance soaked with a solution of an inert strong electrolyte. The salt ions flow through the bridge to complete the cell and balance charges in a solution

182
Q

Electrochemical cell

A

Produces electricity from a chemical reaction

183
Q

Storage cell

A

A cell that can be recharged when the current is passed in the opposite way to the current generated by a chemical reaction in the cell

184
Q

Fuel cell

A

A cell used to harness electricity from a chemical reaction. Chemicals are stored separately outside the cell and fed in when electricity is required.

185
Q

Transition metals

A

d-block elements that form one or more stable ions with incompletely filled d orbitals

186
Q

Complex ion

A

A central metal cation surrounded by Ligands

187
Q

Ligand

A

Atom, ion or molecule that donates a pair of electrons to a central metal ion

188
Q

Cisplatin

A

Pt(NH3)2Cl2 with cis geometry. An anticancer compound that binds the two strands of DNA during the cell division process. This prevents them from separating and hence stops the cell division.

189
Q

Denticity

A

Describes how many dative bonds a ligand can form.

190
Q

Coordination number

A

Number of dative covalent bonds that ligands form with the central metal ion.

191
Q

Ligand exchange

A

A reaction in which a ligand is substituted by another ligand

192
Q

Adsorption

A

The process of forming weak bonds by reactants to a surface of a solid catalyst.

193
Q

Desorption

A

The reverse process to adsorption. Adsorbed molecules leave the surface.

194
Q

Autocatalysis

A

When a product catalyses the reaction.

195
Q

Haemoglobin

A

A protein responsible for oxygen transport in human blood. Contains Fe2+ sure. 4 Haem groups bond to iron in square planar fashion via coordinate bonds. Fifth bond is made from protein bond and iron centre.

196
Q

Rate of reaction

A

Change in concentration of substance per unit of time

197
Q

Rate equation

A

Describes the relationship between the rate of chemical reaction and the concentration/pressure of reagents.

198
Q

Rate constant

A

Relates the rate of a chemical reaction at a given temperature to the product of the concentrations of reactants

199
Q

Orders or a reaction

A

Tells you how the reactants concentration will affect the rate of reaction.

200
Q

Overall order of reaction

A

Sum of all the individual orders of all reactants in a chemical reaction

201
Q

Half life

A

Time taken for the initial amount of reactant to decrease by half

202
Q

Rate determining step

A

The slowest step in a multistep reaction. The overall rate is decided by this step

203
Q

Instantaneous rate

A

A rate found by drawing the tangent to the line of concentrate vs time graph and calculating the gradient of it

204
Q

CFCS

A

Chlorofluorocarbons. Contribute to the depletion of ozone layer. UV light can break down the C-Cl bond and form a chlorine radical.

205
Q

Colorimeter

A

Device for measuring absorbance

206
Q

Absorbance

A

Amount of light absorbed by the solution

207
Q

Chiral centre

A

A carbon atom bearing four different substituents

208
Q

Chirality

A

When a compound and its mirror image are non-superimposable

209
Q

Plane-polarised light

A

Monochromatic light that oscillates in only one plane

210
Q

Polarimeter

A

A device for measuring an angle rotation caused by a chemical.

211
Q

Enantiomers

A

Optical isomers that are mirror images of each other . They rotate the plane of polarisation of plane polarised light

212
Q

Optical activity

A

The ability of a single optical isomer to rotate the plane of polarisation of plane-polarised monochromatic light. An optically active molecule has no planes of symmetry

213
Q

Racemic mixture

A

An equimolar mixture of enantiomers of a chiral compound. Doesn’t rotate plane of polarised light as the two enantiomers cancel out each others light rotating effect. Racemic mixtures are split 50/50

214
Q

Dimer

A

A molecule consisting of two identical molecules linked together

215
Q

Esterification

A

Reaction of an alcohol with a carboxylic acid in the presence of an acid catalyst to form an ester

216
Q

Condensation polymerisation

A

A reaction in which monomers link together to form a large molecule with the additional formation of small molecule.

217
Q

Saponification

A

Refers to the process of making soap. It is a basic hydrolysis of long chain triglycerides to glycerol and corresponding salts of carboxylic acids.

218
Q

Tollen’s test

A

A test that differentiates between aldehydes and ketone. Aldehydes undergo oxidation easily. Ketones do not. Aldehydes reduce tollen’s agent to metallic silver where a mirror can be observed. Ketones do not.

219
Q

Fehling’s and Benedict’s test

A

Test argent is a Cu2+ complex. Aldehyde will undergo a redox reaction to reduce the deep blue copper complex to brick red precipitate.

220
Q

Brady’s reagent

A

2,4-dinitrophenylhydrazine. Used for testing for presence of a carbonyl group. Positive result of bright orange precipitate.

221
Q

Iodoform reaction

A

Used for identification of ethanol, ethanal, methyl ketones and secondary alcohols. Involved warming the compound with iodine and alkaline solution. Positive result is appearance of a yellow crystalline precipitate and characteristic smell.

222
Q

Aromatic

A

Refers to a hydrocarbon ring having delocalised electrons in the pi - framework. Called arenes

223
Q

Kekule model

A

Benzene is made up of planar ring six carbon atoms with alternating single and double bonds between them

224
Q

Delocalised model

A

Two ring shaped electron clouds above and below the plane of six carbon atoms due to the presence of entente pi-framework arising from the overlap of six p orbitals

225
Q

Delocalisation energy

A

Extra stability gained from the delocalised pi-system in benzene

226
Q

Halogen carrier

A

A catalyst (Lewis acid) which helps to introduce the halogen to the aromatic ring by rendering the formation of the electrophile.

227
Q

Amines

A

Derivatives of ammonia, consecutive hydrogens are replaced by a carbon group.

228
Q

Basicity

A

Refers to the extent to which a basic molecule can donate its electron pair to a proton/hydrogen or a water molecule

229
Q

Amino acid

A

Organic compounds containing a carboxylic acid group and an amine group

230
Q

Zwitterion

A

A molecule that contains a positively charged site and a negatively charged site, the overall charge being zero.

Chemistry (14 decks)

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