Flashcards in Definitions Deck (129)
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1
Acid
A species that releases H+ ions in aqueous solution
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Activation Energy
The minimum energy required to start a reaction by the breaking of bonds
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actual yield
the amount of product obtained from a reaction
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addition polymerisation
a formation of a very long molecular chain, by repeated addition of many unsaturated alkenes
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addition reaction
a reaction in which a reactant is added to an unsaturated molecule to make a one saturated molecule
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adsorption
the process that occurs when a gas or a liquid or solute is held to the surface of a solid
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alicyclic
containing carbon atoms joined together in a ring that is not aromatic
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aliphatic
containing carbon atoms joined together in branched (straight) or branched chains
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alkali
a type of base that dissolves in water to release hydroxide ions
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alkanes
the hydrocarbon homologous series with the general formula CnH2n+2
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alkenes
the hydrocarbon homologous series with one double carbon-to-carbon bonds and the general formula CnH2n
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alkyl group
a side chain formed by removing a hydrogen atom removed from and alkane parent chain. Amy alkyl group is often show as 'R'
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alkynes
the hydrocarbon homologous series with one triple carbon-to-carbon bonds and the general formula CnH2n-2
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amount of substance (n)
the quantity whose unit of the mole. chemists use amount of substance as a means of counting atoms
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anhydrous
containing no water molecules
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anion
a negatively charged ion with more electrons than protons
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aromatic
containing one or more benzene rings
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atom economy
(molar mass of products/total molar mass)*100%
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atomic number (z)
the number of protons in the nucleus of an atom(proton number)
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atomic orbital
a region around the nucleus that can hold up to two electrons, with opposite spins
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average bond enthalpy
the average enthalpy change that takes place when breaking by homolytic fission one mole of a given type of bond in the molecules of a gaseous species
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avogadro constant
6.022*10^23 mol^-1, the number of atoms per mole of carbon 12
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avogadro's hypothesis
equal volumes of gases at the same temperature and pressure contain the same number of molecules
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base
a compound that neutralises an acid to form a salt
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binary compound
a compound containing two elements only
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bond angle
the angle between two bonds at an atom
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bonded pair
a pair of electrons shared between to make a covalent bond
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carbocation
an ion that contains a positively charged carbon atom
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catalyst
a substance that increases the rate of a chemical reaction without being used up in the process. A catalyst provides an alternative route for the reaction with a lower activation energy
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cation
a positively charged ion with fewer electrons than protons
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chain reaction
a reaction in which the propagation steps release new radicals that continue the reaction
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cis-trans isomerism
a special type of E/Z isomerism in which there are two non hydrogen groups and two hydrogen atoms around the C-C double bond - the cis isomer (Z isomer) has hydrogen atoms on each carbon on the same side, whilst the trans isomer (E isomer) has hydrogen atoms on each carbon on different sides
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closed system
a system isolated from its surroundings
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collision theory
two reacting particles must collide for a reaction to occur and must be in the correct orientation and have sufficient energy to overcome the activation energy of the reaction
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coordinate bond
a shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only. Also called a dative covalent bond.
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covalent bonding
the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
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dative covalent bond
a shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only; also called a coordinate bond
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dehydration
an elimination reaction in which water is removed from a saturated molecule to make an unsaturated moelcule
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delocalised electrons
electrons that are shared between more than two atoms
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desorption
release of an absorbed substance from a surface
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dipole
a separation in electrical charge so that one atom of a polar covalent bond, has a small positive charge delta+ and the other has a small negative charge delta-
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dipole-dipole force
an attractive force between permanent dipoles in neighbouring polar moleculs
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displacement reaction
a reaction in which a more reactive element displaces a less reactive element from an aqueous solution of its ions
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displayed formula
a formula that shows the relative positioning of all atoms in a molecule and the bonds between them
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disproportionation
a redox reaction in which an element is both oxidised and reduced
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dynamic equilibrium
the equilibrium that exists in a closed system when the rate of teh forward reaction is equal to the rate of the reverse reaction and concentrations do not change
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E/Z isomerism
a type of stereosiomerism in which different groups attached to each carbon of a C=C double bond may be arranged differently in space because of the restricted roatation of the C=C bond
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electron configuration
a shorthand method for showing how electrons occupy sub-shells in an atom
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elecgtronegativity
a measure of the attraction of a bonded atom for the pair of electrons in a covalent bond
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electrophile
an atom or group of atoms that is attracted to an electron-rich centre, where it acceepts a pair of electrons
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electrophilic addition
an adition reaction in which the first step is attack by an electrophile on a region of high electron density
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elimination reaction
the removal of a molecule from a saturated molecule to make an unsaturated molecule
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empirical formula
a formula that shows the simplest whole number ratio of atoms of each element present in a compound
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end point
the point in a titration where the indicator changes colour; the end point indicates when the reaction is just complete
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endothermic reaction
a reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surroundings (deltaH is positive)
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enthalpy
the heat content that is stored in a chemical system
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enthalpy charge (deltaH)
difference in enthalpy between reactants an products in a reaction
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enthalpy cycle
a diagram showing alternative routes between reactants and products which allpws the indirec determination of an enthalpy change from other known enthalpy changes using hess' law
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enthalpy profile diagram
a diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products
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equilibrium constant
a measure of the position of equilibrium; the magnitude of an equilibrium constant indicates whether there are more reactants or more products in an equilibrium system.
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exothermic reaction
a reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants resulting in heat loss to the surroundings (deltaH negative)
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fingerprint region
an area of an infrared spectrum below 1500cm^-1 that gives a characteristic pattern for different compounds
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first ionisation energy
the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
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fractional distillation
the separation of components in a liquid mixture by their different boiling points into fractions with different composition
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fragment ions
ions formed from the breakdown of the molecular ion in a mass spectrometer
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fragmentation
the process in mass spectrometry that cause a positive ion to split into smaller pieces, one of which is a positive fragment ion
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functional group
the part of the organic molecule responsible for its chemical reaction
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general formula
the simplest algebraic formula of a member of a homologous series. For example the general formula of alkanes is CnH2n+2
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giant covalent lattice
a three dimensional structure of atoms, bonded together by strong covalent bonds
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giant ionic lattice
a three dimensional structure of oppositely charged ions bonded together by strong ionic bonds
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giant metallic lattice
a three dimensional structure of positive ions and delocalised electrons, bonded together by strong metallic bonds
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group
a vertical column in the periodic table. elements in a group have similar chemical properties and their atoms have the same number of outer shell electrons
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hess' law
in a reaction take place by more than one route and the initial and final conditions are the same, the total enthalpy change is the same for each route
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heterogeneous catalysis
a reaction in which the catalyst has a different physical state from the reactants; frequently reactants are gases whilst the catalyst is solid
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heterolytic fission
the breaking of a covalent bond with both of the bonded electrons going to each atom, forming a cation (positive ion) and an ion (negative ion)
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homogeneous catalysis
a reaction in which the catalyst and reactants are in the same physical state, which is most frequently the aqueous or gaseous state
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homologous series
a series of organic compounds with the same functional but with each successive member differing by CH2
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homolytic fission
the breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radicals
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hydrated
a crystalline compound containing water molecules
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hydrocarbon
a compound containing carbon and hydrogen only
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hydrogen bond
a strong dipole-dipole attraction between an electron-deficient hydrogen atom of -NH, -OH, or HF on one molecule and lone pair of electrons on a highly electronegative atom containing N, O or F on a different molecule
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hydrolysis
a reaction with water that breaks a chemical compound into two compounds, the H and OH in a water molecule becomes incorporated into the two compounds
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induced dipole-dipole interaction
attractive forces between induced dipoles in different molecules; also called london forces
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initiation
the first stage in a radical reaction in which radical starts when a covalent bond is broken by homolytic fission of a covalent bond
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intermediate
a species formed during a reaction that reacts further and is not present in the final products
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intermolecular forces
an attractive force between molecules. Intermolecular forces can be london forces, permanent dipole-dipole interactions or hydrogen bonding
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ion
a positively or negatively charged atom or a (covalently bonded) group of atoms (a polyatomic ion), where the number of electrons is different from the number of protons
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ionic bonding
the electrostatic attraction between positive and negative ions
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isotope
atoms of the same element with different numbers of neutrons and different masses
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le chatelier's principle
when a system in dynamic equilibrium is subjected to a external change, the system readjusts itself to minimise the effect of the change and to restore equilibrium
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limiting reagent
the reactant that is not in excess which will be used up first and stop the reaction
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london forces
attractive forces between induced dipoles in different molecules; also known as induced dipole-dipole interactions
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lone pair
an outer shell pair of electrons that is not involved in chemical bonding
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mass number A
the sum of the number of protons and neutrons in the nucleus; also known as nucleon number
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metallic bonding
the electrostatic attraction between positive metal ions and delocalised electrons
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concentration
the amount of solute, in mole, dissolved in 1 dm^3 of solution
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molar gas volume
the volume per mole of gas molecules at a stated temperature and pressure
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molar mass
the mass per mole of a substance, in units of gmol^-1
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mole
the amount of any substance containing many elementary particles as there are carbon atoms in exactly 12g of the carbon-12 isotope
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molecular formula
a formula that shows the number and type of atoms of each element present in a molecule
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molecular ion
the positive ion formed in mass spectrometry when a molecule loses an electron
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molecule
the smallest part of a covalent compound that can exist while retaining its chemical identity consisting of two or more atoms covalently bonded together
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monomer
a small molecule that combines with many other monomers to form a polymer
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neutralisation
the reaction between an acid and a base to produce a salt
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nomencalture
a system of naming compounds
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non polar
with no charge seperation across a bond or in a molecule
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nucleon number
the number of protons and neutrons in an atom
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nucleophile
an atom or group of atoms that is attracted to an electron- deficient carbon atom where it donates a pair of electrons to form a new covalent bond
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nucleophilic substitution
a reaction in which a nucleophile is attracted to an electron deficient carbon atom and replaces an atom or group of atoms on it
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oxidation
loss of electrons or an increase in oxidation number
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oxidation number
a measure of the number of electrons that na atom uses to bond with atoms of another element. oxidation number are derived from a set of rules
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oxidation state
the oxidation number
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oxidising agent
a reagent that oxidises another species
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pi bond
a bond formed by the sideways overlap of two p orbitals, containing two electrons and with the electron density concentrated above and below the line joining the nuclei of the bonding atoms
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partial dissociation
the splitting of some of a species in solution into aqueous ions
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pauling electronegativity value
a value assigned as a a measure of the relative attraction of a bonded atom for the pair of electrons in a covalent bond
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percentage yield
actual yield of a product/theoretical yield of a product *100%
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periodicity
a repeating trend in properties of the elements across each period of the periodic table
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period
a horizontal row of elements in the periodic table. elements show trend in properties across a period
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permanent dipole
a small charge difference that does not change across a bond, with positive and negative partial changes on the bonded atoms: the result of the bonded atoms having different electronegatives
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permanent dipole-dipole interactions
attractive forces between the permanent dipoles in different molecules
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polar molecule
a molecule with an overall dipole, having taken into account any dipoles across bonds and the shape of the molecule
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polar covalent bond
a bond with a permanent dipole, having positive and negative partial changes on the bonded atoms
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polyatomic ion
an ion containing more than one atom
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polymer
an large molecule formed from many thousands of repeat units of smaller molecules known as monomers
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position of equilibrium
the relative quantities of reactants and products, indicating the extent of a reversible reaction at equilibrium
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primary
on a carbon atom at the end of a chain
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priamry alcohol
an alcohol in which the -OH. group is attached to a carbon atom that is attached to two or three hydrogen atoms
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