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IB CHEMISTRY – DEFINITIONS (v
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Concentration: the amount of solute per unit of volume of solution
Formula, empirical: The formula obtained by experiment, showing the simplest whole
number ratio of atoms of each element in a particle of a substance
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Formula, structural: Shows the arrangement of atoms and bonds within a molecule
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Molar mass: The mass of a mole of a substance
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Solute: A substance that is dissolved into another (the solvent)
Solvent: a substance that dissolves another (the solute)
Yield, percentage: The experimental yield as a percentage of the maximum theoretical
yield (experimental/theoretical*100)
Topic 2 – Atomic theory
Atomic emission spectra: The characteristic line spectrum that occurs as a result of
energy being released by individual elements
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Atomic absorption spectra: The characteristic line spectrum that occurs as a result of
energy being absorbed by individual elements
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Atomic number: Number of protons in the nucleus
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Hund’s rule: Orbitals within the same sub-shell are filled singly first
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Isotopes: Atoms that contain the same number of protons but a different number of
neutrons
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Pauli’s exclusion principle: electrons in single orbital must have opposite spin
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Relative atomic mass: The weighted mean of all the naturally occurring isotopes of
the element relative to 12C
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Valence electrons: The electrons in the highest main energy level
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Catalyst: A substance that increases the rate of reaction while being recoverable
unchanged at the final stage of the reaction
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Colors are due to e- transitions between different d
orbitals
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Cl- often gives 4 coordinate bonds, CN- gives 6, H2O gives 6 and NH3 gives 4 or 6
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Group: Elements with the same number of valence e-
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Their presence can be detected by the addition of silver nitrate
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Silver halides react with light to form silver metal
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Metalloid: An element that possesses some of the properties of a metal and some of a
non-metal
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Transition element: An element that possesses an incomplete d sub-level in one or
more of its oxidation states
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Form coloured complexes
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Very high m
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and b
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Do not
conduct in any state
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Structure, giant ionic: Hard but brittle
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p
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p
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Structure, giant metallic: Malleable, not brittle
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p
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p
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of
valence e-
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Structure, molecular covalent: Usually soft and malleable unless hydrogen bonded
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p
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p
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Often soluble in non-aqueous solvents,
unless they can hydrogen bond to water
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Diamond is exceptionally hard because there is no plane of weakness in the molecule made up of
sp3 hybridized carbon atoms
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Remaining electrons
after the three σ bonds, are delocalized, resulting in the fact that graphite is a good conductor of
electricity
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The greater the difference, the greater the polarity
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A bond formed by the sideways overlap of p orbitals with electron
densities concentrated above and below a line drawn through the two nuclei
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Bond, σ: Sigma bond
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Single, double and triple bonds have one σ bond
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The electrons are shared and
attracted by both nuclei resulting in a directional bond between the two atoms
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Also
known as coordinate bond
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In an ionic compound the + and – ions are attracted to each other by the electrostatic force between
them, and build up into a strong lattice
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p
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8) in electronegativity
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Must possess
electrons or ions that are free to move
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Forces, dipole-dipole: Permanent electrostatic forces of attraction between polar
molecules
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Forces, Hydrogen bonding: Occurs when hydrogen attached to a highly
electronegative element (N, F, or O) is bonded to another highly electronegative
element (N, F, or O)
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Forces, van der Waal’s: Temporary dipole forces due to momentary unevenness in
spread of electrons
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Increase with increasing molar
mass
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Metallic bonding: The valence electrons in metals become detached from the
individual atoms so that the metals consist of a closely packed lattice of + ions in a
‘sea’ of delocalized electrons
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Molecular polarity: Depends on both the bond polarity and the symmetry
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Can be better explained by delocalization
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VSEPR theory: Valence Shell Electron Pair Repulsion theory
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Greater repulsion between lone pair of electrons than bonded
pairs
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Born-Haber cycle: Energy cycles for the formation of ionic compounds
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Electron affinity: Enthalpy change when an electron is added to an isolated atom in
the gaseous state
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ΔH is +
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Enthalpy: The internal energy stored in the reactants
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Entropy: A measure of the disorder of a system
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ΔH is –
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Gibb’s free energy: Must be – for reaction to be spontaneous
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It is independent of pathway
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The lattice enthalpy increases with
decreasing size of the ions and increasing charge
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Standard conditions: 298 K and 1 atm
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Standard enthalpy of vaporisation: The energy required to vaporise one mole of a
liquid
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Bond dissociation enthalpy: The energy change when one mole of a specific bond is
broken or created under standard conditions
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Standard enthalpy of formation: The energy change when one mole of a compound is
formed under standard conditions from its constituent elements in their standard states
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Topic 6 – Kinetics
Activated complex: Created during a bimolecular process
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Can break down to form either the products or
back to the original reactants
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The other requirement is that the particles have to have an
appropriate geometry of collision
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K=Ae(-Ea/RT)
Bimolecular process: A reaction step when two species collide and interact
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Can be divided into two types: homogenous catalysts are in the same phase as the reactants, while
heterogeneous ones are in a different phase
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Half-life: The time taken for the concentration of the reactant to fall to half of its
initial value
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Order of reaction: The rate is always proportional to the concentration of a reactant
raised to a power, where the power is the order of the reaction with respect to that
reactant
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Rate expression: An equation that shows the relationship between the concentrations
of the reactants and the rate of the reaction
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Rate of reaction: The rate of increase of concentration of one of the products or the
rate of decrease of concentration of one of the reactants
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This determines the rate of the entire reaction
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Topic 7 – Equilibrium
Closed system: A system in which neither matter nor energy can be lost or gained
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Contact process: The synthesis of sulphur trioxide, (V2O5 is used as a catalyst)
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Variable units
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Haber process: The synthesis of ammonia, where Fe is used as a catalyst
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Le Chatelier’s principle: If an equilibrium is subjected to a stress, the equilibrium will
shift to minimize the effect of the stress
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Vapour pressure: The partial pressure of a vapour
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The stronger the intermolecular forces
the lower the vapour pressure at a particular temperature
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Brønsted-Lowry: An acid is defined as a proton donator, while a base is a proton
acceptor
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When a small amount of acid is added, the excess of H+ ions causes the equilibrium to shift to the
left -> balances the difference
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The decrease in [H+] is compensated for by an equilibrium shift to the right
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Buffer solutions are made by several means:
**strong base + excess weak acid; **strong acid + excess weak base; **weak acid + same acid’s
salt; **weak base + same base’s salt
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Conductivity: The more a solution is dissociated into its ions, the greater its
conductivity
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pKa + pKb = pKw
Diprotic: Where one mole of an acid produces two moles of hydrogen ions, e
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H2SO4
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Equimolar: Containing moles at a ratio equal to the stoichiometric ratio
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Exactly
enough to react with each other
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The end point occurs when the pH is approximately equal to

the pKin value
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Lewis theory: An acid is defined as an electron pair acceptor (e
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BF3) and a base is
an electron donator (e
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NH3)
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g
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pH: Power of hydrogen
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Strong: An acid or a base that dissociates completely into its ions
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Some strong acids: hydrochloric, sulphuric, nitric (weaker than other two)
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Water, ionic product of: The equilibrium constant for the dissociation of water into its
ions, where [H2O] is taken to be constant
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Weak: An acid or base that only slightly dissociates into its ions
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Some weak
acids: ethanoic, carbonic
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Topic 9 – Oxidation and Reduction
Anode: Where oxidation takes place
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Cathode: Where reduction takes place
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Electrolysis: Passage of electric current through an electrolyte
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Electrolyte: A substance which does not conduct electricity when solid, but does when
molten or in aqueous solution and is chemically decomposed in the process
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Electroplating: A process of coating one metal with a thin layer of another metal, by
electrolysis
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Oxidation: The loss of electrons
Oxidizing agent: A substance that readily oxidizes other substances
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Reactivity: A measure of the readiness of a substance to gain or lose electrons
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Redox reaction: A reaction in which there is a transfer of electrons, i
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reduction and
oxidation occurring simultaneously
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Reducing agents
are thus oxidized
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Paper dipped in a
saturated solution of KNO3 is an example of a salt bridge
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Example: Cu(s)/Cu2+(aq) || H+(aq) / H2(g)
Standard conditions: 298 K, 1 atm, 1
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Standard electrode potential: The electrode potential of one half-cell compared against
another half-cell, by convention, the hydrogen half-cell, which is arbitrarily given a
value of 0 V
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Standard hydrogen electrode: Arbitrarily assigned a potential of zero
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Voltaic cell: Two different half-cells connected together to enable to electron
transferred during the redox reaction to produce energy in the form of electricity
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Topic 10 – Organic Chemistry
Benzene: Hexagonal shape with delocalized π bonds
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Boiling and melting point: Depend on intermolecular forces
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forces, the higher the m
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and b
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Bromination: Yellow/orange bromine is decolorized when added to an alkene due to
addition reaction
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Carbocation: A cation in which the carbon carries most of the + charge
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Chiral center: An asymmetric carbon atom, i
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has four different groups of atoms
attached to it
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Commonly polar
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Dehydration: Loss of water
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Esterification: Process by which an alcohol and a carboxylic acid are converted into
an ester and water, with sulphuric acid catalysis
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Fission, homolytic: Bond breaking in which each atom takes one of the e- in the bond,
creating free radicals
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Very reactive
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Undergo SN2 mechanism in nucleophilic
substitution
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Undergo SN1 mechanism in nucleophilic
substitution
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Have similar chemical properties, but gradually changing physical properties
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Ethanol can be formed from addition of water to ethene
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Hydrogenation: Addition of hydrogen
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Hydrolysis: Process by which a molecule is broken down by water
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Isomers, functional group: Where the isomers contain different functional groups
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Isomers, optical: Where a molecule shows optical activity in its mirror images
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Occurs
when there is one or more chiral centers
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Isomers, stereo-: Where the molecules have a different spatial arrangement of atoms
and hence different 3D shapes
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Isomers, structural: Where the atoms have a different structural formula altogether
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Mechanism, SN1: A unimolecular process by which a halogenoalkane undergoes
nucleophilic substitution
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Faster than SN2, as the formation of the
intermediate carbocation is faster than the SN2 route which involves a transition state
with relatively high activation energy
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Mechanism involves formation of a transition state which
involves both of the reactants
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Nucleophile: The species that donates the electron pair in an organic chemical
reaction
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Typical nucleophiles are CN-, OH- and
NH3
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Peptide bond: -C=ONH-
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Peptide, di-: Two amino-acids joined together
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Peptide: Molecule formed by aminoacids joined together by peptide bonds (by
condensation reaction in which water is lost)
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Polymerization, addition: Forming a polymer by addition of monomers
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Reaction, addition: A reaction in which the reactant is added across a C=C bond,
converting it to a C-C bond
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Addition reactions with hydrogen use Ni as catalyst
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Substitution reactions with halogenoalkanes are nucleophilic substitutions
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Reflux: A condenser which causes any vapour produced to condense and returns to
the flask and continues to react
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On the other hand, if the aldehyde
is desired, this can be distilled from the reaction mixture as soon as it is formed
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Alkanes are saturated
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Spectroscopy, IR: Analyzing the bonds present within a molecule by sending infrared
light through it, causing the bonds to absorb radiation of characteristic frequencies
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Trans-isomer: The geometric isomer in which the similar groups are on different sides
of the double bond
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Unsaturated: Containing double bonds between carbon aoms
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Can be tested for by bromination

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