definitions Flashcards
1
Q
atomic number
A
the number of protons in the nucleus of an atom
2
Q
bohr model
A
describes an atom as a small dense nucleus with electrons orbiting around the nucleus. this model explains different periodic properties of atoms
3
Q
electron
A
a negatively charged subatomic particle which orbits the nucleus at various energy levels. the relative mass of an electron is 1/1836
4
Q
ion
A
a charged atom or molecule
5
Q
isotopes
A
atoms of the same element with he same number of protons and electrons but a different number of neutrons. isotopes of an element have different masses
6
Q
mass number
A
the total number of protons and neutrons in the nucleus of an atom
7
Q
mass spectrometry
A
the total number of protons and neutrons in the nucleus of an atom an instrument which gives accurate information about relative isotopic mass and the relative abundance of isotopes
8
Q
neutron
A
a neutral subatomic particle found in the nucleus of an atom. the relative mass of a neutron is 1
9
Q
proton
A
a positively charged subatomic particle found in the nucleus of an atom. the relative mass of a proton is1
10
Q
relative abundance
A
the amount of one substance compared with another
11
Q
relative atomic mass
A
the weighted mean mass of an atom compared with 1/12th mass of an atom of carbon-12
12
Q
relative isotopic mass
A
the mass of an atom of an isotope compared with 1/12th mass of an atom of carbon-12
13
Q
relative formula mass
A
the mass of the formula unit of a compound with a giant structure
14
Q
relative molecular mass (Mr)
A
the mass of a simple molecule
15
Q
ammonium ion
A
an ion with the formula NH3 ^+^
16
Q
carbonate
A
an ion with the formula CO3 ^2-^
17
Q
hydroxide
A
an ion with the formula OH ^-^
18
Q
ionic compound
A
a compound which is made up of oppositely charged ions that are held together by electrostatic forces
19
Q
nitrate
A
an ion with the formula NO3 ^-^
20
Q
silver ion
A
has the formula Ag ^+^
21
Q
state symbols
A
symbols within a chemical equation which indicate the state of each compound under the reaction conditions. (g) gaseous, (l) liquid, (s) solid, and (aq) aqueous
22
Q
sulfate
A
an ion with the formula SO4 ^2-^
23
Q
zinc ion
A
has the formula Zn ^2+^
24
Q
amount of substance
A
the quantity that has moles as its units, used as a way of counting atoms. the amount of substance can be calculated using mass (n=m/M), gas volume (n=pV/RT), or solution volume and concentration (n=CV)
25
anhydrous
a crystalline compound containing no water
26
atom economy
a measure of the amount of starting materials that end up as useful products. a high atom economy means a process is more sustainable as there is less waste produced
27
avogadro constant (NA)
the number of particles per mole of substance (6.02 x 10^23 mol^-1)
28
composition by mass
the relative mass of each element in a compound
29
empirical formula
the simplest whole number ratio of atoms of each element present in a compound
30
hydrated
a crystalline compound that contains water
31
ideal gas
a gas which has molecules that occupy negligible space with no interactions between them. the ideal gas equation is pV=nRT
32
molar gas volume
the volume of 1 mol of gas (units=dm^3mol^-1)
33
molar mass
mass per mole of a substance (units=gmol^-1)
34
mole (mol)
the amount of any substance containing as many particles as there are carbon atoms in exactly 12g of carbon-12 isotope
35
molecular formula
the number and type of atoms of each element in a molecule
36
percentage yield
the percentage ratio of the actual yield of product from a reaction compared with the theoretical yield
37
relative molecular mass
the average mass of one molecule of an element or compound compared to 1/12th the mass of an atom of carbon-12
38
stoichiometry
the relative quantities of substances in a reaction
39
water of crystallisation
water molecules that form part of the crystalline structure of a compound
40
acid
compound that release H+ ions in aqueous solution
41
alkali
water soluble bases. alkalis release OH- ions into aqueous solutions
42
base
a substance that can accept H+ ions from another substance
43
neutralisation
a reaction between H+ and OH-, forming water. this may be a reaction between an acid and a base to form a salt
44
strong acid
an acid that completely dissociates in solution
45
titration
a technique used to determine the amount of one solution of a known concentration required to completely react with a known volume of another solution of unknown concentration
46
weak acid
an acid that only partially dissociates in solution
47
oxidation
loss of electrons/increase in oxidation number
48
oxidation number
a number that represents the number of electron lost or gained by an atom of an element. a positive oxidation number indicates the loss of electrons
49
redox reaction
a reaction in which one element is oxidised and another is reduced
50
reduction
gain of electrons/decrease in oxidation number
51
atomic orbital
a region of space around the nucleus that can hold up to 2 electrons with opposite spins. there is 1 orbital in the s subshell, 3 orbitals in the p subshell, an 5 orbitals in the d subshell. orbitals are filled in order of increasing energy, with orbitals of the same energy occupied singly before pairing
52
electronic configuration
the arrangement of electrons into orbitals and energy levels around the nucleus of an atom/ion
53
energy level
the shell that an electron is in
54
shell
the orbit that an orbital is i around the nucleus of an atom. the shell closest to the nucleus is the first shell. the outermost shell that is occupied by electrons is the valence shell
55
subshell
a subdivision of the electronic shells into different orbitals. the types of subshell are s, p, d, and f
56
average bond enthalpy
the average energy required to break a bond, used as a measurement of the strength of a covalent bond. the average bond enthalpy is measured using a variety of molecules that contain a specific bond
57
bonding pair
a pair of outer-shell electrons involved in bonding
58
covalent bond
a strong bond formed between 2 atoms due to the electrostatic attraction between a shared pair of electrons and the atomic nuclei
59
dative covalent (coordinate) bond
a type of covalent bond in which both of he electrons in the shared pair come from one atom
60
electronegativity
the ability of an atom to attract bonding electrons in a covalent bond. this is often quantified using Pauling’s electronegativity increases towards F in the periodic table
61
electron pair repulsion theory
pairs of electrons around a nucleus repel each other so the shape that a molecule adopts has these pairs of electrons positioned as far apart as possible. lone pairs offer more repulsion than bonding pairs as they are closer to the nucleus of the central atom
62
hydrogen bonding
a type of intermolecular bonding that occurs between molecules containing N, O, or F and a H atom of -NH, -OH, or HF. a lone pair on the electronegative atom (N, O, or F) allows the formation of a hydrogen bond
63
intermolecular forces
interactions between different molecules. types of intermolecular forces include permanent dipole-dipole interactions and induced dipole-dipole interactions as well as hydrogen bonding
64
ionic bond
electrostatic attraction between positive and negative ions
65
ionic compounds
compounds made up of oppositely charged ions. these compounds generally have high melting and boiling points. typically, ionic compounds are soluble and can conduct electricity when liquid or aqueous (not when solid)
66
ionic lattice
a giant structure in which oppositely charged ions are strongly attracted in all directions
67
linear
the shape of a molecule in which the central atom has 2 bonding pairs
68
london (dispersion) forces
induced dipole-dipole interactions caused when the random movement of electrons creates a temporary dipole in one molecule which then induces a dipole in a neighbouring molecule
69
lone pair
a pair of outer-shell electrons not involved in bonding
70
macroscopic properties
properties of a bulk material rather than the individual atoms/molecules that make up the material
71
non-linear
the shape of a molecule in which the central atom has 2 bonding pairs and 2 lone pairs
72
octahedral
the shape of a molecule in which the central atom has 6 bonding pairs
73
permanent dipole
a permanent uneven distribution of charge
74
polar bond
a covalent bond that has a permanent dipole due to the different electronegativities of the atoms that make up the bond
75
polar bond
a molecule that contains polar bonds with dipoles that don’t cancel out due to their direction (must be unsymmetrical)
76
pyramidal
the shape of a molecule in which the central atom has 3 bonding pairs and 1 lone pair
77
simple molecular lattice
a solid structure made up of covalently bonded molecules attracted by intermolecular forces. these compounds generally have relatively low melting and boiling points and are typically insoluble in water but soluble in organic solvents. molecular substances don’t conduct electricity
78
tetrahedral
the shape of a molecule in which the central atom has 4 bonding pairs
79
trigonal bipyramidal
the shape of a molecule i which the central atom has 5 bonding pairs
80
trigonal planar
the shape of a molecule in which the central atom has 3 bonding pairs
81
cations
positively charged ions
82
d-block
the part of the periodic table in which the elements have their highest energy electron in a d-orbital
83
first ionisation energy
the removal of one mole of electrons from one mole of gaseous atoms. factors which affect the first ionisation energy are: strength of attraction between the electron and the nucleus, nuclear charge, and the atomic radius. these is a small decrease in first ionisation energy due to s- and p-subshell energies (between Be and B) and p-orbital repulsion (between N and O)
84
giant covalent lattice
a network of atoms bonded by strong covalent bonds. giant covalent lattices are typically insoluble with a high melting and boiling point due to the presence of strong covalent bonds. they are also poor electrical conductors as they don’t contain mobile charged particles
85
giant metallic lattice structure
the structure of all metals, made up of cations and delocalised electrons. giant metallic structures are typically insoluble with a high melting and boiling points due to strong electrostatic forces of attraction between cations and electrons. metals are good electrical conductors due to the presence of delocalised electrons
86
group
a column in the periodic table
87
melting point
the temperature at which a solid melts and becomes a liquid. this increases from giant metallic to giant covalent structures then decreases to simple molecular structures
88
metallic bonding
strong electrostatic attraction between cations and delocalised electrons
89
p-block
the part of the periodic table in which the elements have their highest energy electron in a p-orbital
90
period
a row in the periodic table
91
periodicity
a repeating trend in physical and chemical properties across the periods of the periodic table
92
s-block
the part of the periodic table in which the element have their highest energy electron in an s-orbital
93
successive ionisation energies
the energy required to remove each electron one-by-one from one mole of gaseous atoms/ions
94
group 2 oxide
a compound with the general formula MO, where M is a group 2 element. when group 2 oxides react with water, they form a alkaline solution, with alkalinity increasing down the group
95
second ionisation energy
the removal of one mole of electrons from one mole of gaseous 1+ ions to form one mole of 2+ ions
96
boiling point
the temperature at which a liquid boils and becomes a gas
97
diatomic molecules
molecules that are made up of 2 atoms. halogens are diatomic
98
displacement reaction
a reaction in which one atom is replaced by another. halogens can undergo displacement reactions as their reactivity decreases down the group. the more reactive halogen will displace the less reactive halogen from a solution of its salt
99
disproportionation
the oxidation and reduction of the same element
100
induced dipole-dipole interactions
forces of attraction between molecules caused when the random movement of electron creates a temporary dipole in one molecule which then induces a dipole in a neighbouring molecule
101
precipitation reaction
a reaction in which two aqueous solutions are combined to form an insoluble salt (a precipitate). halide anions undergo precipitation reactions with aqueous silver ions
102
water treatment
the addition of chlorine to water to kill bacteria. the risks associated with the use of chlorine to treat water are the hazards of toxic chlorine gas and the possible risks from the formation of chlorinated hydrocarbons
103
anion
a negatively charged ion
104
halide
a salt containing a group 7 anion. Cl-, Br-, and I- can be tested for using a collusion of silver ions a this reaction forms a coloured precipitate. the solubility of the precipitate is then tested using dilute and concentrated ammonia
105
qualitative analysis
identifies the elements present in a substance, typically using test-tube reactions
106
activation energy
the minimum energy required for a reaction to take place
107
endothermic
a reaction which takes in energy (ΔH is positive). more energy is required to break bonds than is released by making them
108
enthalpy (H)
a value that represents the heat content of a system
109
enthalpy change (ΔH)
the change in the heat content of a system during a reaction. this can be determines from experimental results using q=mc ΔT
110
enthalpy change of combustion (ΔcH)
the enthalpy change that takes place when one mole of a substance is completely combusted
111
enthalpy change of formation (ΔfH)
the enthalpy change that takes place when one mole of a compound is formed form its elements
112
enthalpy change of neutralisation (ΔneutH)
the enthalpy change that takes place when one mole of water is formed from a neutralisation reaction
113
enthalpy change of reaction (ΔrH)
the enthalpy change that is associated with a particular chemical equation
114
enthalpy profile diagram
shows the difference in the enthalpy of reactants and products as well as the activation energy of a reaction
115
exothermic
a reaction which gives out energy (ΔH is negative. more energy is released by bond making than is used in bond breaking
116
Hess’ law
the enthalpy change of a reaction is independent of the route it takes
117
standard conditions
a pressure of 100kPa and a temperature of 298K
118
standard state
the physical stage (s, l, g, aq) of a substance under standard conditions
119
Boltzmann distribution
a graph showing the distribution of the energies of molecules in relation to the activation energy. increasing temperature will increase the proportion of molecules with energy above the activation energy. a catalyst lowers the activation energy meaning more molecules will have sufficient energy to react
120
catalyst
a substance that speeds up the rate of a reaction without being used up. a catalyst allows the action to proceed via a different route with a lower activation energy. catalysts are importunate in terms of economics and sustainability as they enable processes to take place at lower temperatures, meaning less energy is required
121
collision theory
the theory which states that molecules must collide with sufficient energy at the correct orientation for a reaction to occur
122
concentration
the amount of a substance that is dissolves per unit volume of solution. increasing the concentration increases the rate of reaction as there are more molecules in the same volume, meaning more frequent successful collisions
123
heterogeneous catalyst
a catalyst that is in a different state to the reactants
124
homogeneous catalyst
a catalyst which is in the same state as the reactants
125
pressure
the force that a gas exerts on the walls of a container. increasing the pressure increases he rate of reaction as there are more molecules in the same volume, meaning more frequent successful collisions
126
rate of reaction
a measure of how quickly a reactant is used up/a product is formed. rate can be determined by measuring concentration, the volume of gas produces or the mass lost over time
127
compromise
balancing several different factors in order to get the best possible outcome
128
dynamic equilibrium
a closed system in which the rates of the forward and reverse reactions are equivalent. the concentrations of reactants and products don’t change
129
homogeneous equilibrium
an equilibrium in which all reactants are in the same state
130
le chatelier’s principle
when a system in dynamic equilibrium is subject to change, the position of equilibrium will shift to minimise the change. this principle is used to determine the effect of changing pressure, temperature, or concentration on the position of equilibrium
131
Kc
the equilibrium constant that is equal to the concentration of products raised to their stoichiometric coefficients divided by the concentration of reactants to the power to their stoichiometric coefficients. hen Kc is greater then 1, the equilibrium favours the products. when Kc is less than 1, the equilibrium favours the reactants
132
alicyclic
an aliphatic compound that is arranged in non-aromatic rings (with or without side chains)
133
aliphatic
a compound containing carbon and hydrogen atoms joined in straight or branched chains or in non-aromatic rings
134
alkane
a homologous series with the general formula C_n_H_2n+2_
135
alkyl
a group with the general formula C_n_H_2n+1_
136
aromatic
an organic compound containing a benzene ring
137
curly arrow
shows the movement of a pair of electrons. curly arrows must start from a bond, a lone pair of electrons, or a negative charge
138
dipole
a partial charge on an tom which is caused by the differing electronegativities of atoms in a covalent bond
139
displayed formula
the relative positions of atoms and the bonds between them
140
functional group
a group of atoms responsible for the characteristic reactions of a compound
141
general formula
the simplest algebraic formula of a member of a homologous series
142
heterolytic fission
when a covalent bond breaks, one bonding atom receives both electrons from a bonding pair
143
homologous series
a series of organic compounds containing the same functional group with successive members differing by. -CH2
144
homolytic fission
when a covalent bond breaks, each bonding atom receives one electron from the bonding pair, forming 2 radicals
145
organic compound
a carbon-containing compound
146
radial
a species with an unpaired electron
147
reaction mechanism
a series of steps that represent the overall reaction by showing the breaking and forming of bonds using curly arrows
148
saturated
an organic compound which only contains C-C single bonds
149
skeletal formula
the simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving the carbon skeleton and the functional groups
150
structural formula
the minimal detail that shows the arrangement of atoms in a molecule
151
structural isomers
compounds with the same molecular formula but different structural formulae
152
unsaturated
an organic compound which contains a least one C=C double bond, triple bond, or an aromatic ring
153
σ-bond
a type of covalent bond which forms when atomic orbitals overlap head-on. sigma (σ) bonds can rotate freely
154
complete combustion
when a compound is brunt in a plentiful supply of oxygen. when alkanes are completely combusted, the only products are water and carbon dioxide
155
hydrocarbon
a compound which contains hydrogen and carbon atoms only
156
incomplete combustion
when a compound is burnt in a limited supply of oxygen. when alkanes are incompletely combusted, water, carbon monoxide, particulates, and some carbon dioxide may be produced
157
initiation
the first step in a radical substitution mechanism, involving the formation of the radicals
158
propagation
the intermediate steps in a radical substitution mechanism where a radical reacts with anther species
159
radical substitution
a type of institution reaction in which a radical replaces another atom/group of atoms in a compound. alkanes can undergo radical substitution reactions with chlorine or bromine in the presence of UV light, forming a mixture of organic products
160
termination
the final steps in a radical substitution mechanism in which 2 radicals react together to form a species which only contains paired electrons
161
π-bond
a type of covalent bond formed when adjacent p-orbitals overlap sideways above and below the bonding C atoms. pi (π) bonds can’t be rotated. as π-bonds have low bond enthalpy, alkanes are more reactive than alkanes
162
addition polymerisation
the formation of a long chain molecule when many monomers join together
163
addition reaction
a reaction in which molecules combine to form a single product
164
alkanes
an organic compound containing at least one C=C double bond
165
biodegradable
a substance that can be decomposed by bacteria or other living organisms
166
CIP priority rules
a set of rules used to identify whether a stereoisomer is E or Z. atoms with a higher atomic number have higher priority. if the highest priority substituents are on the same side of the double bond (both above or below), its a Z isomer, whereas if the highest priority groups are on opposite sides (one above and one below), its the E isomer
167
cis-trans isomerism
a type of E/Z isomerism in which the two substituent groups attached to the carbon atoms are the same. according to the CIP priority rules, cis isomers have the highest priority substituents on the same side of the double bond (both above or below) while trans isomers have hem on opposite sides (one above and one below)
168
electrophile
an electron pair acceptor
169
electrophilic addition
a reaction in which a π bond is broken an 2 new σ bonds form as a result of the addition of an electron pair acceptor
170
E/Z isomerism
a type of stereoisomerism caused by the restricted rotation of π bonds. two different groups must be attached to each carbon atom of the C=C group. according to the CIP priority rules, Z isomers have the highest priority substituents on the same side of the double bond (both above or below) while E isomers have them on opposite sides (one above and one below)
171
markownikoff’s rule
used to redact what the major product of an addition reaction will b when H-X is added to an unsymmetrical alkene. H attaches to the less substituted carbon to generate the more stable carbocation intermediate
172
monomer
a small molecule that is used to form polymers
173
photodegradable
a substance that can be broken down by light
174
polymer
a large molecule made from many small units that have been bonded together
175
primary carbocation
a molecule in which the carbon with the positive charge is only attached to one alkyl group. this is the least stable carbocation
176
repeat unit
a structure within the polymer that appears over and over again. joining many repeat units together would form the polymer
177
secondary carbocation
a molecule in which the carbon with the positive charge is attached to two alkyl groups. this is more sable than a primary carbocation but less stable than a tertiary carbocation
178
stereoisomers
compounds with the same structural formula but a different arrangement of atoms in space
179
tertiary carbocation
a molecule in which the carbon with the positive charge is attached to three alkyl groups. this is the most stable type of carbocation
180
alcohol
an organic compound containing the OH functional group. the polarity of the OH functional group means that alcohols can form hydrogen bonds and are soluble in water (when the alkyl chain is short). in addition, alcohols have a relatively low volatility compared with alkanes
181
aldehyde
an organic compound containing the -CHO functional group. aldehydes can be formed from the oxidation of primary alcohols using acidified dichromate and distillation
182
combustion
a rapid exothermic reaction of a substance with oxygen
183
elimination
a type of reaction in which 2 atoms/groups of atoms are removed from a molecule
184
haloalkanes
an organic compound containing a halogen atom (F/Cl/Br) bound to an alkyl chain. haloalkanes can be formed from alcohols via a substitution reaction with halide ions in the presence of acid
185
ketone
an organic compound containing the C=O functional group in the middle of an alkyl chain. ketones can be formed by the oxidation of a secondary alcohol
186
oxidising agent
a substance that can oxidise another species while being reduced
187
primary alcohol
an alcohol in which the OH is attached to a primary carbon atom. primary alcohols can be oxidised to form either an aldehyde or a carboxylic acid, depending on the conditions
188
secondary alcohol
an alcohol in which the OH is attached to a secondary carbon atom. secondary alcohols can be oxidised under reflux with acidified dichromate to form a ketone
189
tertiary alcohol
an alcohol in which the OH is attached to a tertiary carbon atom. tertiary alcohols cannot be oxidised
190
CFC
a class of compound made up o carbon, fluorine, and chlorine, used as refrigerants and aerosol propellants. CFCs can be broken down by UV light in the upper atmosphere to form chlorine radicals which catalyse the breakdown of ozone
191
hydrolysis
the breakdown of a compound as a result of a reaction with water
192
nucleophile
an electron pair donor
193
nucleophilic substitution
a reaction in which an electron pair donor attacks an electrophilic atom to replace an atom/group of atoms
194
ozone
a molecule with the formula O3, which absorbs UV light in the atmosphere. he breakdown of ozone can be catalysed by chlorine radicals as well as other radicals
195
anhydrous salt
a salt such as MgSO4 or CaCl2, which is used to remove traces of water from an organic solution
196
distillation
a technique in which a liquid is heated then the vapour is cooled and collected in a separate flask to the reaction mixture. during distillation, the condenser must be positioned horizontally
197
redistillation
a technique used to purify an organic liquid using multiple distillations
198
reflux
the continual boiling and condensing of a reaction mixture. this is to ensure that the reaction goes to completion. during reflux, the condenser must be positioned vertically
199
separating funnel
a piece of apparatus that is used to purify an organic liquid by removing the organic layer from an aqueous layer
200
synthetic route
a series of steps that are followed to make a specific compound
201
elemental analysis
a sample is analysed to determine the proportion of elements that make up the compound present. this is done by converting a known amount of an unknown sample into simple known compounds
202
fragmentation
during mass spectrometry, unstable molecular ions break down into smaller fragments
203
fragment ions
smaller ions formed when an unstable molecular ion breaks down during mass spectrometry
204
infrared radiation
a type of electromagnetic radiation that is absorbed by covalent bonds, causing them to vibrate at a specific frequency
205
infrared spectroscopy
a technique used to identify particular bonds and functional groups within a molecule
206
M+1 peak
a small peak on a mass spectrum caused by the presence of a small proportion of carbon-13
207
M/Z ratio
the mass to charge ratio on a mass spectrum. this is equivalent to the mass of an ion
208
molecular ion peak
the pea on a mass spectrum with the highest m/z value, used to determine molecular mass of a compound
209
arrhenius equation
k=Ae^-Ea/RT^
210
clock reaction
a reaction in which the time taken for an abrupt visible change to occur is measured. the abrupt change typically indicates the formation of the product
211
colorimetry
a technique used to measure the amount of light absorbed by a solution, used to determine the rate of reaction
212
first order reactant
doubling the concentration of a first order reactant will double the rate
213
rate constant (k)
a constant value that relates the rate of a reaction at a given temperature to the concentrations of the reactanats
214
rate-determining step
the slowest step of a reaction
215
second order reactant
doubling the concentration will quadruple the rate
216
zero order reactant
doubling the concentration will have no impact on the rate
217
Kp
the equilibrium constant that is equal to the partial pressures of the products raised to the power of their stoichiometric coefficients divided by the partial pressures of the reactants raised to the power of their stoichiometric coefficients
218
partial pressure
the pressure that would be exerted by one gas in a mixture if it occupied the container alone. P_A_=PX_A_
219
acid dissociation constant (Ka)
the extent of acid dissociation. pKa=-log(Ka) and Ka=10^-pKa^
220
buffer solution
a system that minimises pH change on addition of small amounts of an acid or base. a buffer solution can be formed from a weak acid and a salt of the weak acid or from excess weak acid and a strong alkali
221
dibasic acid
an acid that can donate 2 hydrogen atoms per molecule of the acid
222
ionic product of water (Kw)
the temperature dependent constant that represents the dissociation of water into H+ and OH-
223
monobasic acid
an acid that can donate 1 hydrogen atom per molecule of acid
224
pH
a way of communicating the concentration of hydrogen ions pH=-log[H+] and [H+]=10^-pH^
225
born-haber cycle
a cycle which can be used to calculate the lattice enthalpy of an ionic compound using other enthalpy changes
226
conservation of energy
the total energy of an isolated system remains constant
227
enthalpy change of atomisation (ΔHat)
the enthalpy change that takes place when one mole of gaseous ions is formed from an element in its standard state
228
enthalpy change of hydration (ΔHhyd)
the enthalpy change that takes place when one mole of gaseous ions are dissolved in water (exothermic). increasing ionic charges and decreasing ionic radii make this value more negative as there would be greater attraction between the water molecules and the ions
229
enthalpy change of solution (ΔHsol)
the enthalpy change that takes place when one mole of solute is dissolved
230
first electron affinity
the amount of energy released when one mole of electrons is added to one mole of gaseous ions, forming one mole of 1- ions
231
lattice enthalpy (ΔHLE)
the formation of one mole of an ionic lattice from gaseous ions. lattice enthalpy is used as a measure of the strength of ionic bonds in a giant lattice, with a more negative value meaning stronger bonds. increasing ionic charges and decreasing ionic radii make this value more negative as there wold be greater attraction between the ions
232
entropy (S)
a measure of the dispersal of energy in a system. the greater the entropy, he more disordered the system. the order of entropy is solids
233
free energy change (ΔG)
the feasibility of a process depends on entropy change, temperature, and enthalpy change. the equation for gibbs free energy is ΔG= ΔH-T ΔS. a process is spontaneous/feasible when ΔG is negative. gibbs free energy doesn’t consider kinetics
234
kinetics
the part of chemistry relating to rates of reaction
235
cell potential
a measure of the potential difference between two half cells, calculated by combining 2 standard electrode potentials. the calculated cell potential can be used to predict feasibility of a reaction, although this doesn’t consider concentration or kinetics
236
electrochemical cell
contains electrodes in an electrolyte and is used to generate current. a cell could be made up of either a metal or non-metal in contact with a solution of its ions or a solution of ions of the same element in different oxidation states with a Pt electrode. if the cell is a standard cell, ions of the same element should have a concentration of 1 moldm^-3^
237
equimolar solution
a solution of ions in high there is an equal number of moles of each ion
238
fuel cell
a type of cell that requires a constant supply of fuel and oxygen in order to generate a potential difference
239
half equation
an equation which shows the number of electrons that are transferred during a reaction
240
standard electrode potential
the e.m.f. of a half cell compared with a standard hydrogen half cell. this is measured under standard conditions
241
storage cell
a type of cell that can store energy. storage cells convert chemical energy into electrical energy by a reaction and they may be recharged by reversing the chemical reaction
242
bidentate ligand
a substance that can form 2 dative covalent bonds with a metal ion/metal
243
cis-platin
the cis-isomer of Pt(NH3)2Cl2, used as an anti cancer drug. cis-platin binds to DNA, preventing cell replication
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complex ion
an ion which has a central metal atom (typically a transition element) surrounded by ligands. the ligands are bound to the transition metal centre by dative coordinate bonds
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coordination number
the number of dative covalent bonds formed between ligands and a metal ion centre
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haemoglobin
a protein which is important for oxygen transport in blood. the iron in haemoglobin undergoes a ligand substitution reaction involving CO2 and O2
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ligand substitution
a reaction in which one ligand in a transition metal complex is replaced by another. typically these reactions are associated with a colour change
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monodentate ligand
a substance that can form 1 dative covalent bond with a metal ion/metal
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optical isomer
compounds that have the same structural formulae but are mirror images of one another
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transition elements
d-block elements that can form an ion with an incomplete d-subshell. transition elements have more than one oxidation state, form coloured ions, and can act as catalysts
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acyl chloride
a molecule containing the COCl functional group
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aromatic compound
a compound containing at least one benzene ring
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delocalised model of benzene
the p-orbitals of the 6 carbon atoms overlap to form a delocalised π system. this model is supported by experimental evidence: all the C-C bond lengths in benzene are the same, the enthalpy change of hydrogenation is less exothermic than would be expected for cyclohex-1,3,5-triene and the benzene does not undergo addition reactions
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electron density
a representation of the probability of finding an electron at a specific point around an atom/molecule
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electron donating groups
groups which donate electrons into the aromatic ring when they are attached to a carbon in the ring
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electron withdrawing groups
groups which pull electron density away from the delocalised π system of benzene
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electrophilic substitution
a reaction in which an electrophile reacts with another compound to replace an atom/group of atoms
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haloalkane
an organic compound containing a halogen atom bound to an alkyl chain
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halogen carrier
a Lewis acid that can bind to a halogen molecule, weakening the halogen bond and allowing the halogen to function as an electrophile and attack electrons in an aromatic ring
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Kekulé’s structure of benzene
a model of benzene which contains altering C=C double bonds and C-C single bonds in a hexagonal ring, with each carbon atom bound to one hydrogen atom
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phenol
an aromatic ring with an OH group attached
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2,4-DNP
also known as Brady’s reagent, this compound forms an orange precipitate in the presence of aldehydes and ketones. the melting point of the 2,4-DNP derivative of a carbonyl can be used to identify the carbonyl compound
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aldehyde
a compound containing the -CHO functional group at the end of an alkyl chain
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carbonyl
the C=O group. aldehydes and ketones are carbonyl compounds
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nucleophile
an electron pair donor
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nucleophilic addition
a reaction in which an electrophilic π bond reacts with a nucleophile, breaking the π bond and forming 2 new σ bonds
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Tollens’ reagent
also known as ammoniacal silver nitrate, this reagent forms a silver mirror in the presence of an aldehyde and can be used to distinguish between aldehydes and ketones
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brønsted-lowry acid
a proton donor
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brønsted-lowry base
a proton acceptor
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carboxylic acid
an organic compound containing the -COOH functional group
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ester
a compound containing the R-COO-R functional group
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esterifictaion
the process of making esters
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water soluble
a compound that can dissolve in water
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aliphatic amine
an amine which only contains straight or branches alkyl chains
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amines
compounds that contain the NR_3_ functional group
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aromatic amine
an amine which contains a benzene ring directly attached to the nitrogen atom
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α-amino acid
a compound with the general formula RCH(NH2 ) COOH, where an amino group and a carboxylic acid group are bonded to the same carbon atom
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amine group
the -NH_2_ group in an organic compound
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chiral centre
a carbon atom which is bonded to 4 different groups
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optical isomerism
a type of stereoisomerism in which compounds are non-superimposablemirror images of one another
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amide hydrolysis
amides can either be hydrolysed under acidic conditions (forming carboxylic acids and ammonium salts) or under alkaline conditions (forming carboxylate salts and either ammonia or an amine)
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condensation polymerisation
a long chain molecule formed when monomers react together with the release of small molecules such as water
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ester hydrolysis
esters can either be hydrolysed with hot aqueous acid (forming carboxylic acids and alcohols) or with hot aqueous alkali (forming carboxylate salts and alcohols)
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acylation
a reaction that is used to form substituted aromatic compounds, using an acyl
chloride to form a C-C bond in the presence of a halogen carrier
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acid hydrolysis
the breakdown of a compound using aqueous acid
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alkylation
a reaction which is used to form substituted aromatic compounds, using a haloalkane to form a C-C bond in the presence of a halogen carrier
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Friedel-Crafts reactions
reactions which were developed to attach substituents to an aromatic ring
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nitrile
an organic compound which contains a -C≡N group bound to an alkyl chain
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distillation
a technique in which a liquid is heated then the vapour is cooled and collected in a separate flask to the reaction mixture. during distillation, the condenser must be positioned horizontally
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filtration under reduced pressure
a technique used to separate and dry an organic solid. a Büchner funnel is inserted into the top of a side-arm flask and a vacuum is applied. the solution is poured onto filter paper in the Büchner funnel so that the solid product can be separated
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recrystallisation
a technique used to purify an organic solid. the sample is dissolved in the minimum volume of hot solvent and filtered. the filtrate is then cooled before being filtered under reduced pressure. the purified solid will collect on the filter paper in the Büchner funnel
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reflux
the continual boiling and condensing of a reaction mixture. this is to ensure that the reaction goes to completion. during reflux, the condenser must be positioned vertically
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synthetic route
a series of steps that are followed to make a specific compound
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chromatography
a technique used to separate and identify components in a mixture. there are several different types of chromatography, including: thin layer chromatography, and gas chromatography. separation during chromatography depends on the balance between solubility in the mobile phase and retention by the stationary phase
295
gas chromatography
a type of chromatography in which a column is packed with a solid (or a solid coated in a liquid) and a gas is passed through the column under pressure at high temperature. mass spectrometry may be used to analyse components separated by GC
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mobile phase
a substance that moves through the chromatography system to separate the mixture. this may be a gas (GC) or a liquid (TLC)
297
qualitative analysis
techniques that are used to identify whether or not an element, functional group or ion is present in a sample
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retention time
the time taken for a sample to travel from the inlet to the detector in GC. the recorded retention time can be compared with standards to identify the substances in the mixture
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Rf value
in TLC, the Rf values can be calculated as shown below then compared with standards to identify what substances present in a mixture.
Rf = distance moved by substance ÷ distance moved by solvent
300
stationary phase
a substance through which the mobile phase moves in chromatography. this is typically a solid although a solid coated in a liquid may be used in GC
301
thin layer chromatography (TLC)
a type of chromatography in which a plate is coated with a solid and a solvent moves up the plate
302
carbon-13 NMR spectroscopy
the shift of a carbon or proton environment relative to standard (TMS). thr chemical shift value (δ) depends on the molecular environment of the proton/ carbon atom
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coupling
interaction between adjacent non-equivalent protons during NMR spectroscopy
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D2O exchange
as O-H and N-H peaks can appear across a wide range of chemical shift values on a proton NMR spectrum, D2O exchange can be used to identify which peaks are caused by O-H and N-H protons. firstly, a proton NMR is run on a sample. the sample is then shaken with D2O and a second proton NMR is run. any peaks that are due to O-H or N-H protons will disappear on the second spectrum as these protons will be exchanged for deuterium
305
deuterated solvent
solvent, such as CDCl3 , in which all of the hydrogen atoms have been replaced by deuterium (^2^H )
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doublet
a signal on a H NMR spectra made up of 2 peaks, indicating that there is 1 adjacent non-equivalent proton
307
elemental analysis
a sample is analysed to determine the proportion of elements that make up the compound present. this is done by converting a known amount of an unknown sample into simple known compounds
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environment
in NMR spectroscopy, a proton or carbon environment considers the atoms/ groups that are adjacent to that hydrogen/ carbon atom. if 2 protons / carbons are surrounded by different groups of atoms, they are in different environments
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equivalent protons
protons that are in the same environment
310
IR spectroscopy
a technique used to identify particular bonds and functional groups within a molecule. infrared radiation is absorbed by covalent bonds in molecules, causing them to vibrate at a specific frequency
311
mass spectroscopy
a technique used to identify compounds and determine relative molecular mass by measuring their mass to charge ratio
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n+1 rule
used to determine spin-spin splitting patterns of adjacent non-equivalent protons. a proton with n adjacent non-equivalent protons will have a signal made up of n+1 peaks on a H NMR spectrum
313
quartet
a signal on a H NMR spectra made up of 4 peaks, indicating that there are 3 adjacent non-equivalent protons
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triplet
a signal on a H NMR spectra made up of 3 peaks, indicating that there are 2 adjacent non-equivalent protons
