Definitions Flashcards
Isotope
Atoms with the same number of protons but a different number of neutrons
Atomic Number
Number of protons in the nucleus
Mass Number
Number of protons and neutrons in the nucleus
Ion
A positively or negatively charged single atom or covalently bonded group of atoms
Relative Isotopic Mass
The mass of an atom of an isotope compared with one twelfth of the mass of carbon-12
Relative Atomic Mass
The weighted mean mass of an atom of an element compared to one twelfth of the mass of carbon-12
Avogadro’s Constant
The number of atoms per mole of the carbon-12 isotope
Mole
The amount of any substance containing as many particles as there are particles in 12g of the carbon-12 isotope
Relative Formula Mass
The weighted mean mass of the formula unit of a compound compared with one twelfth of an atom of carbon-12
Empirical Formula
The simplest whole number ratio of atoms of each element present in a compound
Molecular Formula
The actual number of atoms of each element in a molecule
Molar Volume
The volume per mole of a gas
At rtp it is 24 dm^3/mol
Concentration of a solution
The amount of solute in mol, dissolved in 1dm^3 of solution
Stoichiometry
The molar relationship between the relative quantities of substances taking part in a reaction
% Yield
Actual Yield / Theoretical Yield
Atom Economy
Molar mass of desired products / Sum of molar masses of all products
Aufbau Principle
Electrons fill the sub levels in order of increasing energy
Hund’s Rule
Within a sub level, the orbitals are first occupied singly by unpaired electrons
Ionic Bonding
The electrostatic attraction between positive and negative ions
Covalent Bonding
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
Bond Length
The distance between the nuclei of two bonded atoms
Bond Angle
The angle between two covalent bonds
Electronegativity
The measure of its tendency to attract the electron pair(s) from a covalent bond
Permanent Dipole
A small charge difference that does not change across a bond, with partial charges on the bonded atoms
Hydrogen Bonding
A strong dipole-dipole attraction between a hydrogen atom bonded to O, N or F and a lone pair on O, N or F
First Ionisation Energy
The energy required to remove one mole of electrons from one mole of gaseous atoms
Oxidation Number
A measure of the number of electrons that an atom uses to bond with atoms of another element
Oxidation
Loss of electrons or an increase in oxidation number
Reduction
Gain of electrons or a decrease in oxidation number
Oxidising Agent
A reagent that oxidises another species and is itself reduced.
Reducing Agent
A reagent that reduces another species and is itself oxidised.
Disproportionation
A redox reaction in which the same element is both oxidised and reduced
Law of the Conservation of Energy
Energy cannot be created or destroyed, just converted from one form to another
Enthalpy
The heat content that is stored in a chemical system
Enthalpy Change
The heat exchanged with the surroundings during a chemical reaction
The difference between the enthalpy of the products and the reactants
Exothermic
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings
Endothermic
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken out of the surroundings
Standard State
The state an element or compound will exist in at standard temperature and pressure
Standard Enthalpy Change of Combustion
The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, with all the reactants and products in their standard state
Standard Enthalpy Change of Reaction
The enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions, with all reactants and products in their standard states
Standard Enthalpy Change of Neutralisation
The enthalpy change that accompanies the reaction of an acid by a base to form one mole of H2O under standard conditions, with all the reactants and products in their standard states
Average Bond Enthalpy
Energy required to break one mole of a specific type of bond in a gaseous molecule
Hess’ Law
If a reaction can take place by more than one route and the initial and final concentrations are the same, the total energy is the same for each route
Enthalpy Change of Formation
The enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states
Reaction Rate
The change in concentration of a reactant or product in a given time
whats a Catalyst
A substance that increases the rate of a chemical reaction without being used up in the process
Activation Energy
The minimum energy required to start a reaction by the breaking of bonds
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
Le Chatelier’s Principle
When a system in dynamic equilibrium is subjected to external change, the system readjusts itself to minimise the effect of the change and restore equilibrium
Closed Systen
A system isolated from its surroundings
Equilibrium Constant
A measure of the position of equilibrium
Homogeneous
In the same phase
Heterogeneous
Different phases
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
Half Life
The time taken for the concentration of the reactant to be reduced by half
Reaction Mechanism
A series of steps that together make up the overall reaction
Rate Determining Step
The slowest step in the reaction mechanism of a multi step reaction
Mole Fraction
Number of mole of species / total number of moles of all species
Partial Pressure
Mole fraction x total pressure
what is Lattice Enthalpy
Lattice enthalpy is the change in enthalpy that accompanies the formation of one mole of ionic compound from its gaseous ions under standard conditions
Standard Enthalpy Change of Atomisation
The change in enthalpy that accompanies the formation of one mole of gaseous atoms from the element in the standard state
what is the First Electron Affinity?
the First Electron Affinity is the change in enthalpy that accompanies the formation of one mole of gaseous 1- ions from gaseous atoms
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
Standard Enthalpy Change of Hydration
The enthalpy change that takes place when one mole of isolated gaseous ions is dissolved in water forming one mole of aqeuous ions under standard conditions
whats Standard Entropy
The quantitative measure of the degree of disorder in a system
Standard Entropy Change of Reaction
The entropy change that accompanies a reaction in the molar quantities expressed in the chemical equation under standard conditions, all reactants and products being in their standard states
Free Energy Change
The balance between enthalpy, entropy and temperature for a process
Redox
A reaction in which both reduction and oxidation take place
Standard Electrode Potential
The emf of a half cell compared with a standard hydrogen half cell, measured at 298K with solution concentrations of 1 mol/dm^3 and a gas pressure of 1 atm
Brønsted-Lowry Acid
a Brønsted-Lowry Acid donates a proton
Brønsted-Lowry Base
It accepts a proton
Conjugate Acid
Brønsted-Lowry base that accepted a proton
Conjugate Base
a conjugate base is the Brønsted-Lowry acid that donated a proton
Acid Dissociation Constant
The equilibrium constant that shows the extended of dissociation of a weak acid
what’s the PH equation?
PH= -log(10)[H+]
Weak Acid
Partial dissociation of hydrogen atoms
Strong Acid
Complete dissociation of hydrogen atoms
Ionic product of water equation?
Kw = [H+][OH-]
Buffer Solution
A system that minimises pH changes on addition of small amounts of an acid or a base
Transition Metal
A d-block element that forms an ion with an incomplete d sub-shell
Complex Ion
A transition metal ion bonded to ligands by coordinate bonds (dative covalent bonds)
Coordination Number
The number of coordinate bonds attached to the central metal ion
Ligand
A molecule or ion that can donate a pair of electrons to the transition metal ion to form a coordinate bond
what is Denticity?
The number of separate sites in a molecule or ion that can donate an electron pair to a transition metal ion
Monodentate
A ligand that can donate one electron pair to a transition metal ion
what’s Bidentate?
A ligand that can donate two electron pairs to a transition metal ion
Tridentate
A ligand that can donate three electron pairs to a transition metal ion
Stereoisomerism
Species with the same structural formula but with a different arrangement in space
what are Optical Isomers / Enantiomers?
Optical Isomers / Enantiomers are Non-super imposable mirror images of each other
Ligand Substitution
A reaction in which one or more ligands in a complex ion are replaced by different ligands
