A2 Definitions Flashcards
Adic dissociation constant Ka
The equilibrium constant that shows the externt of dissociation of a weak acid.
For a weak acid HA,
Ka=[H+(aq)][A-]/[HA(aq)]
Acid-base pair
A pair of two species that transform into each other by gain or loss of a proton
Bronsted-Lowry acid
A species that is a proton, H+, donor
Bronsted-Lowry base
A species that is a proton, H+, acceptopr
Buffer solution
A system that minimises pH changes on addition of small amounts of an acid or a base
Chemical shift
A scale, in ppm, that compares the frequency of an NMR absorption with the frequencey of the reference TMS at delta=0ppm.
Chiral Carbon
A carbon atom attached to four different atoms or groups of atoms
Chromatogram
A visible record showing the result of separation of the components of a mixture by chromatography
Complex ion
A transition metal ion bonded to ligands by coordinate bonds (Dative covalent bonds)
Concentration
The amount of solute, in moles, dissolved in 1dm^3 (1000cm^3) of solution
Condensation reaction
A reaction in qhich two small molecules react together to form a larger molecule with elimination of a small molecule such as water
COnjugate acid
A species that releases a proton to form a conjugate base
Conjugate base
A species that accepts a proton to form a conjugate acid
Coordination number
The total number of coordinate bonds formed between a central metal ion and ligandsa
Electrophilic substitution
A type of substitution reaction in which an electrophile is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond,
Ethantiomers
Stereoisomers that are non-superimposable mirror images of each other
ALSO KNOWN AS OPTICAL ISOMERS
End point
The point in a titreation where the indicator changes colour’ the end point indicates when the reaction is just complete
Entropy S
The used for the dispersal of energy and disorder within the chemicals making up a chemical sustem
Equivalence point
The point in a titration atr which the volume of one solution has reacted exactly with the volume of the second solution
Esterification
A reaction in which a carboxylic acid reacts with an alcohol to form an ester and water
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 gasesous 1- ions
First ionisation energy
The energy reqwuired to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole og gaseous 1+ ions
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 og gaseous 1+ ions
Free energy change DeltaG
The balance between enthalpy, entroly and temperature for a process gfiven by
DeltaG=DeltaH-TDeltaS
PROCESS IS FEASIBLE WHEN DELTAG<0
Half life3
The time taken for the concentration of a reactant t decrease by halg
Heterogeneous equilibrium
An equilibrium uin which the species making up the reactants and products have different physical states
Homogeneous equilibrium
An equilibrium in which all the species making up the reactants and products have the same physical state
Hydrolysis
A rA 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
Initial rate of reaction
The change inconcentration of a reactant or product per unit time at the start of the reaction t=0
Ionic product of water Kw
The product of the ions formed in the partial dissociation of water given by K1=[H+(aq)][OH-(aq)]
Lattice enthalpy
The enthalpy change that accompanies the formatio of one mole of an ionic compound from its gaseous ions under standard conditions
Ligand
A molecule or ion that cvan donate a pair of electrons to the transitino metal ion
Ligand substritution
A reaction in which one or more ligands in a complex ion are replaced by different ligands
Mobile phase
The phase that moves in chromatography
Optical isomers
Stereoisomers that arae non superimposable mirror images of each other
ALSO CALLED ENANTIOMERSS
Order
The power to which the concentration of a reactant is raised in the rate equation
Overall order
The sum of the individual orders of reactants in the rate equation m+n
pH
The expression
pH=-log[H+(aq)]
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
Rate constant k
The constant that links the rate of reaction with the concentrations of the reactants raised to the powers of their orders in the rate equation
Rate equation
For a reaction: A+B->C with orders m for A and n for B, the rate equation is given by
rate=k[A]^m[B]^n
Rate=determining step
The slowest step in the reaction mechanism of a multi-step reaction
Retention time
In gas chromatography, the time for a component to pass from the column inlet to the detector
Rf value
Distance moved by component divided by the distance moved by solvent
component/solvent
Second electron affinity
The enthalpy chgange that takes place when one elecvtron is added to each ion in one mole og gaseous 1- ions to form one mole of gaseous 2- ions
Second ionisation energy
The energy required to remove one electron from each ion in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions
Spin-spin coupling
In an NMR spectrum, the interaction between spin states of non-equivalent nuclei that results in the splitting of a signal
Standard conditions
A pressure of 100kPa, a stated temperature, usually 298K (25degreesC) and a concentration of 1 moldm-3 and a gas pressure of 100kPa
Standard enthalpy chgange of atomisation
The enthalpy change that takes place when one mole of gaseous atoms form s frrom the element in its standard state
Standard enthalpy change of formation DeltafH
The enthalpyu change that takes place when one mole of a compound is formed from its consitituent elements in their standard states uinder standar5d condition
Standard enthalpu change of hydration
The enthalpy change that takes place when one mole of isolated gaseous ions is dissolbed in water forming one mole of aqueous ions under standard conditions
Standard enthalpyu change of solution
The enthalpy change that takes place when one mole of a compound is completely dissolved in watrerr under standard conditions
Stationary phase
The phase that does not move in chromatography
Transition element
A d-block elemtnt which forms an ion with an incomplete d sub-shell
