A2 Definitions

Question 1

Adic dissociation constant Ka

Answer 1

The equilibrium constant that shows the externt of dissociation of a weak acid.
For a weak acid HA,
Ka=[H+(aq)][A-]/[HA(aq)]

Question 2

Acid-base pair

Answer 2

A pair of two species that transform into each other by gain or loss of a proton

Question 3

Bronsted-Lowry acid

Answer 3

A species that is a proton, H+, donor

Question 4

Bronsted-Lowry base

Answer 4

A species that is a proton, H+, acceptopr

Question 5

Buffer solution

Answer 5

A system that minimises pH changes on addition of small amounts of an acid or a base

Question 6

Chemical shift

Answer 6

A scale, in ppm, that compares the frequency of an NMR absorption with the frequencey of the reference TMS at delta=0ppm.

Question 7

Chiral Carbon

Answer 7

A carbon atom attached to four different atoms or groups of atoms

Question 8

Chromatogram

Answer 8

A visible record showing the result of separation of the components of a mixture by chromatography

Question 9

Complex ion

Answer 9

A transition metal ion bonded to ligands by coordinate bonds (Dative covalent bonds)

Question 10

Concentration

Answer 10

The amount of solute, in moles, dissolved in 1dm^3 (1000cm^3) of solution

Question 11

Condensation reaction

Answer 11

A reaction in qhich two small molecules react together to form a larger molecule with elimination of a small molecule such as water

Question 12

COnjugate acid

Answer 12

A species that releases a proton to form a conjugate base

Question 13

Conjugate base

Answer 13

A species that accepts a proton to form a conjugate acid

Question 14

Coordination number

Answer 14

The total number of coordinate bonds formed between a central metal ion and ligandsa

Question 15

Electrophilic substitution

Answer 15

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,

Question 16

Ethantiomers

Answer 16

Stereoisomers that are non-superimposable mirror images of each other
ALSO KNOWN AS OPTICAL ISOMERS

Question 17

End point

Answer 17

The point in a titreation where the indicator changes colour’ the end point indicates when the reaction is just complete

Question 18

Entropy S

Answer 18

The used for the dispersal of energy and disorder within the chemicals making up a chemical sustem

Question 19

Equivalence point

Answer 19

The point in a titration atr which the volume of one solution has reacted exactly with the volume of the second solution

Question 20

Esterification

Answer 20

A reaction in which a carboxylic acid reacts with an alcohol to form an ester and water

Question 21

First electron affinity

Answer 21

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

Question 22

First ionisation energy

Answer 22

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

Question 23

First ionisation energy

Answer 23

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

Question 24

Free energy change DeltaG

Answer 24

The balance between enthalpy, entroly and temperature for a process gfiven by
DeltaG=DeltaH-TDeltaS
PROCESS IS FEASIBLE WHEN DELTAG<0

Question 25

Half life3

Answer 25

The time taken for the concentration of a reactant t decrease by halg

Question 26

Heterogeneous equilibrium

Answer 26

An equilibrium uin which the species making up the reactants and products have different physical states

Question 27

Homogeneous equilibrium

Answer 27

An equilibrium in which all the species making up the reactants and products have the same physical state

Question 28

Hydrolysis

Answer 28

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

Question 29

Initial rate of reaction

Answer 29

The change inconcentration of a reactant or product per unit time at the start of the reaction t=0

Question 30

Ionic product of water Kw

Answer 30

The product of the ions formed in the partial dissociation of water given by K1=[H+(aq)][OH-(aq)]

Question 31

Lattice enthalpy

Answer 31

The enthalpy change that accompanies the formatio of one mole of an ionic compound from its gaseous ions under standard conditions

Question 32

Ligand

Answer 32

A molecule or ion that cvan donate a pair of electrons to the transitino metal ion

Question 33

Ligand substritution

Answer 33

A reaction in which one or more ligands in a complex ion are replaced by different ligands

Question 34

Mobile phase

Answer 34

The phase that moves in chromatography

Question 35

Optical isomers

Answer 35

Stereoisomers that arae non superimposable mirror images of each other ALSO CALLED ENANTIOMERSS

Question 36

Order

Answer 36

The power to which the concentration of a reactant is raised in the rate equation

Question 37

Overall order

Answer 37

The sum of the individual orders of reactants in the rate equation m+n

Question 38

pH

Answer 38

The expression | pH=-log[H+(aq)]

Question 39

Precipitation reaction

Answer 39

The formation of a solid from a solution during a chemical reaction. Precipitates are often formed when two aqueous solutions are mixed together

Question 40

Rate constant k

Answer 40

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

Question 41

Rate equation

Answer 41

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

Question 42

Rate=determining step

Answer 42

The slowest step in the reaction mechanism of a multi-step reaction

Question 43

Retention time

Answer 43

In gas chromatography, the time for a component to pass from the column inlet to the detector

Question 44

Rf value

Answer 44

Distance moved by component divided by the distance moved by solvent component/solvent

Question 45

Second electron affinity

Answer 45

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

Question 46

Second ionisation energy

Answer 46

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

Question 47

Spin-spin coupling

Answer 47

In an NMR spectrum, the interaction between spin states of non-equivalent nuclei that results in the splitting of a signal

Question 48

Standard conditions

Answer 48

A pressure of 100kPa, a stated temperature, usually 298K (25degreesC) and a concentration of 1 moldm-3 and a gas pressure of 100kPa

Question 49

Standard enthalpy chgange of atomisation

Answer 49

The enthalpy change that takes place when one mole of gaseous atoms form s frrom the element in its standard state

Question 50

Standard enthalpy change of formation DeltafH

Answer 50

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

Question 51

Standard enthalpu change of hydration

Answer 51

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

Question 52

Standard enthalpyu change of solution

Answer 52

The enthalpy change that takes place when one mole of a compound is completely dissolved in watrerr under standard conditions

Question 53

Stationary phase

Answer 53

The phase that does not move in chromatography

Question 54

Transition element

Answer 54

A d-block elemtnt which forms an ion with an incomplete d sub-shell