Inorganic and foundations definitions Flashcards
Define acid
A speices that releases H+ ions in aqueous solution
Define acid dissociation constant Ka
The equilibrium constant that shows the extent of dissociation of a weak acid.
For weak acid HA Ka=[H+ (aq)] [A-(aq)] / [HA(aq)]
Define acid-base pair
A pair of two species that transform into each other by gain or loss of a proton
Define activation energy
The minimum energy required to start a reaction by the breaking of bonds
Actual yield
The amount of product obtained from a reaction
Addition reaction
A reaction in which a reactant is added to an unsaturated molecule to make one saturated molecule
Define adsorption
The process that occurs when a gas or liquid or solute is held to the surface of a solid
Define alkali
A type of base that dissolves in water forming hydroxide ions
Define amount of substance
The quantity whose unit of the mole, used as a means of counting any species such as atoms, ions and molecules
Define anhydrous
Containing no water molecules
Define anion
A negatively charged ion with more electrons than protons
Define atom economy
Atom economy= (Sum of molar masses of desired products)/ (Sum of molar masses of all products) *100
Define atomic number
The number of protons in the nucleus of an atom
Define atomic orbital
A region around the nucleus that can hold up to two electrons with opposite spins
Define average bond enthalpy
The average enthalpy change that takes place when breaking by homolytic fission 1 mol of a given type of bond in the molecules of a gaseous species
Define Avogadro constant
The number of atoms per mole of the carbon-12 isotope (6.023*10^23 mol-1)
Define base
A proton acceptor. A compound that neutralises an acid to form a salt
Define binary compound
A compound containing two elements only
Define bonded pair
A pair of electrons shared between two atoms to make a covalent bond
Define buffer solution
A system that minimises pH changes on addition of small amounts of an acid or base
Define 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 lower activation energy
Define cation
A positively charged ion with fewer electrons than protons
Define closed system
A system isolated from its surroundings
Define 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
Define complex ion
A transition metal ion bonded to ligands by coordinate bonds
Define concentration
The amount of solute, in mols dissolved in 1 dm3 of solution
Define conjugate acid
A species that releases a proton to form a conjugate base
Define a conjugate base
A species that accepts a proton to form a conjugate acid
Define 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
Define coordination number
THe total number of coordinate bonds formed between a central metal ion and ligands
Define covalent bond
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
Define dative covalent
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
Define dehydration
An elimination reaction in which water is removed from a saturated molecule to make an unsaturated one
Define delocalised electrons
Electrons that are shared between more than two atoms
Define desorption
Release of an adsorbed substance from a surface
Define dipole
A separation in electrical charge so that one atom of a polar covalent bond, or one end of a polar molecule has a small positive charge and the other has a small negative charge
Define displacement reaction
A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of its ions
Define disproportionation
A redox reaction in which the same element is both oxidised and reduced
Define dynamic equilibrium
The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and concentrations do not change
Define E/Z isomerism
A type of stereoisomerism in which different groups attached to each carbon of a C=C double bond may be arranged differently in space because of the restricted rotation of the C=C bond
Define electronegativity
A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond
Define elimination reaction
The removal of a molecule from a saturated molecule to make an unsaturated molecule
Define enantiomers
Stereoisomers that are non-superimposable mirror images of each other; also called optical isomers
Define end point
The point in a titration where the indicator changes colour; the endpoint indicated when the reaction is just complete
Define 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
Define enthalpy
The heat content that is stored in a chemical system
Define enthalpy change
The difference between the enthalpy of the products and the enthalpy of the reactants
Define enthalpy cycle
A diagram showing alternative routes between reactants and products which allows the indirect determination of an enthalpy change from other known enthalpy changes using Hess’s law
Define entropy
Used to describe the dispersal of energy and disorder within the chemicals making up the chemical system
Define equilibrium constant
A measure of the position of equilibrium; the magnitude of an equilibrium indicates whether there are more reactants or more products in an equilibrium system
Define equivalence point
The point in a titration at which the volume of one solution has reacted exactly with the volume of the second solution
Define 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
Define first electron affinity
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
Define 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
Define free energy change deltaG
The balance between enthalpy, entropy and temperature for a process.
Given by ΔG= ΔH-T ΔS
A process is feasible when ΔG<0
Define giant covalent lattice
A 3d structure of atoms, bonded together by strong covalent bonds
Define giant ionic lattice
A 3d structure of oppositely charged ions bonded together by strong ionic bonds
Define giant metallic lattice
A 3d structure of of positive ions bonded together by strong metallic bonds
Define 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
Define half-life
The time taken for the concentration of a reactant to decrease by half
Define hess’s law
If a reaction can take place by more than one route and the initial and final conditions are the same, the total energy change is the same for each route
Define heterogeneous catalysis
A reaction in which the catalyst has a different physical state from the reactants; frequently reactants are gases whilst the catalyst is a solid
Define heterogeneous equilibrium
An equilibrium in which the species making up the reactants and products have different physical states
Define 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
Define homogeneous equilibrium
An equilibrium in which all the species making up the reactants and products have the same physical state
Define hydrated
A crystalline compound containing water molecules
Define hydrogen bond
A strong dipole-dipole attraction between an electron-deficient hydrogen atom of -NH, -OH, -HF on one molecule and a lone pair of electrons on a highly electronegative atom containing N,O or F on a different molecule
Define induced dipole-dipole interactions
Attractive forces between induced dipoles in different molecules- London forces
Define initial rate of reaction
The change in concentration of a reactant or product per unit time at the start of the reaction: t=0
Define intermolecular force
An attractive force between molecules. Intermolecular forces can be London forces, permanent dipole-dipole interactions or hydrogen bonding
Define ionic bonding
The electrostatic attraction between positive and negative ions
Define ionic product of water Kw
The product of the ions formed in partial dissociation of water.
Kw= [H+ (aq)][OH-(aq)]
Define isotopes
Atoms of the same element with different numbers of neutrons and different masses but the same number of protons
Define lattice enthalpy
The enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions
Define 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 chage and to restore equilibrium
Define ligand
A molecule or ion that can donate a pair of electrons to the transition metal ion
Define ligand substitution
A reaction in which one or more ligands in a complex ion are replaced by different ligands
Define limiting reagent
The reactant that is not in excess, which will be used up first and stop the reaction
Define lone pair
An outer shell pair of electrons that is not involved in chemical bonding
Define metallic bond
The electrostatic attraction between positive metal ion sand delocalised electrons
Define molar gas volume
The volume per mole of gas molecules at a stated temperature and pressure
Define molar mass
The mass per mole of a substance in units g mol-1
Define mole
The amount of any substance containing as many elementary particles as there are carbon atoms in exactly 12g of the carbon-12 isotope that is, 6.02*10^23 particles
Define 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,
Define neutralisation
A chemical reaction in which an acid and a base react together to produce a salt
Define optical isomers
Stereoisomers that are non-superimposable mirror images of each other; also known as enantiomers
Define order
The power to which the concentration of a reactant is raised in the rate equation
Define overall order
The sum of the individual orders of reactants in the rate equation
Define oxidation
Loss of electrons of an increase in oxidation number
Define oxidation number
A measure of the number of electrons that an atom uses to bond with atoms of another element.
Define oxidising agent
A reagent that oxidises another species
Define pi-bond
A bond formed by the sideways overlap of two p-orbitals, with the electron density above and below the plane of the bonding atoms
Define percentage yield
percentage yield= (amount in mol, of a product)/ (theoretical amount, in mol, of product) *100
Define period
A horizontal row of elements in the periodic table. Elements show trends in properties across a period
Define periodicity
A repeating trend in properties of the elements across each period of the periodic table
Define permanent dipole
A small charge difference that does not change across a bond, with delta positive and delta negative partial charges on the bonded atoms: the result of the bonded atoms having different electronegativities
Define permanent dipole-dipole interactions
An attractive force between permanent dipoles in neighbouring polar molecules
Define pH
pH= -log[H+(aq)]
Define polar molecule
A molecule that has an overall dipole taking into account all dipoles across bonds and the shape of molecules.
Define polyatomic ion
An ion containing more than one atom
Define position of equilibrium
The relative quantities of reactants and products, indicating the extent of a reversible reaction at equilibrium
Define precipitation reaction
The formation of a solid from a solution during a chemical reaction. Precipitates are often formed when two aqueous solutions are mixed together
Define rate constant k
The constant that links the rate of reaction with the concentration of the reactants raised to the powers of their orders in the rate equation
Define rate equation
For a reaction A+B→C with orders m for A and n for B, the rate equation is give by; rate=k[A]^m[B]^n
Define rate of reaction
The change in concentration of a reactant or product in a given time
Define rate-determining step
The slowest step in the reaction mechanism of a multi-step reaction
Define redox reaction
A reaction involving both reduction and oxidation
Define reducing agent
A reagent that reduces another species
Define reduction
Gain of electrons or a decrease in oxidation number
Define reflux
The continual boiling and condensing of a reaction mixture back to the original container to ensure that the reaction takes place without the contents of the flask burning dry
Define relative atomic mass
The weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of carbon-12
Define relative formula mass
The weighted mean mass of the formula unit of a compound compared with 1/12 of the mass of an atom of carbon-12
Define relative isotopic mass
The mass of an atom of an isotope compared with 1/12 of the mass of an atom of carbon-12
Define relative molecular mass
The weighted mean mass of a molecule of a compound compared with 1/12 of the mass of an atom of carbon-12
Define reversible reaction
A reaction that takes place in both forward and reverse directions
Define sigma bond
A bond formed by the end on overlap of one orbital from each bonding atom, consisting of two electrons and with the electron density centred around a line directly between the nuclei of the two atoms.
Define salt
The product of a reaction in which the H+ ions from the acid are replaced by metal or ammonium ions
Define shell
A group of atomic orbitals with the same main energy level
Define shielding effect
The repulsion between electrons in different inner shells. Shielding reduces the net attractive force between the positive nucleus and the outer shell electrons
Define specific heat capacity
The energy required to raise the temperature of 1g of a substance by 1 degrees
Define spectator ions
Ions that are present but take no part in a chemical reaction
Define standard conditions
A pressure 100kPa
Temperature 298 K
Concentration 1 mol dm-3
Define standard electrode potential
The e.m.f of a half cells compared with a standard hydrogen half-cell, measured under standard conditions
Define standard enthalpy change of atomisation
The enthalpy change that takes place when one mole of gaseous atoms are formed from its elements in their standard state
Define standard enthalpy change of combustion
The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, all reactants and products being in their standard states
Define standard enthalpy change of formation
Enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions
Define standard enthalpy change of hydration
The enthalpy change that takes place when one mole of gaseous ions is dissolved in water forming one mole of aqueous ions under standard conditions
Define standard enthalpy change of neutralisation
The enthalpy change that accompanies the reaction of an acid by a base to form one mole of H2O (l), under standard conditions, with all reactants and products in their standard states
Define standard enthalpy change of reaction
The enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products being in their standard states
Define standard enthalpy change of solution
The enthalpy change that takes place when one mole of a compound is completely dissolved in water under standard conditions.
Define stereoisomers
Compounds with the same structural formula but with a different arrangement of the atoms in space
Define stoichiometry
The ratio of the amount, in mols, of each substance in a chemical equation
Define strong acid
An acid that dissociates completely in solution
Define structural isomers
Molecules with the same molecular formula but a different structural formula
Define sub-shell
A group of orbitals of the same type within a shell
Define substitution reaction
A reaction in which an atom or group of atoms is replaced with a different atom or group of atoms
Define surroundings
Everything that is not the chemical system
Define system
The chemicals involved in the reaciton
Define theoretical yield
The yield resulting from complete conversion of reactants to products
Define thermal decomposition
The breaking up of a chemical substance with heat into at least two chemical substances
Define transition element
A d-block element which forms at least 1 stable ion with an incomplete d sub-shell
Define volatility
The ease at which a liquid turns into a gas. Volatility increases as boiling point decreases
Define water of crystallisation
Water molecules that are bonded into a crystalline structure of a compound
Define weak acid
An acid that dissociated only partially in solution
