Definitions Year 2

Question 1

acid dissociation content (Kₐ)

Answer 1

Equilibrium constant that shows extent of dissociation of a weak acid.

Question 2

acid

Answer 2

Species that releases H+ ions in aq solution

Question 3

acid-base pair

Answer 3

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

Question 4

Bronsted-Lowry acid

Answer 4

species that is a proton (H+) donor

Question 5

Bronsted-Lowry base

Answer 5

species that is a proton (H+) acceptor

Question 6

buffer solution

Answer 6

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

Question 7

chemical shift

Answer 7

A scale, in ppm, that compares frequency of an NMR absorption with the frequency of reference TMS (0 ppm)

Question 8

chiral carbon

Answer 8

carbon atom attached to four different atoms or groups of atoms

Question 9

chromatogram

Answer 9

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

Question 10

complex ion

Answer 10

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

Question 11

concentration

Answer 11

amount of solute (in moles) dissolved in 1dm3 of solution

Question 12

condensation reaction

Answer 12

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

Question 13

conjugate acid

Answer 13

a species that releases a proton to form a conjugate base

Question 14

conjugate base

Answer 14

a species that accepts a proton to form a conjugate acid

Question 15

coordination number

Answer 15

Total number of coordinate bonds formed between a central metal ion and ligands (not number of ligands)

Question 16

electrophilic substitution

Answer 16

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 17

enantiomers

Answer 17

Stereoisomers that are non-superimposable mirror images of each other, (aka Optical Isomers)

Question 18

end point

Answer 18

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

Question 19

entropy (S)

Answer 19

The dispersal of energy, disorder and randomness within a chemical system

Question 20

equivalence point

Answer 20

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

Question 21

esterification

Answer 21

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

Question 22

first electron affinity

Answer 22

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

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 of gaseous 1+ ions

Question 24

free energy change (ΔG) & equation

Answer 24

The balance between enthalpy, entropy and temperature for a process given by
ΔG = ΔH - TΔS

Question 25

feasibility

Answer 25

ΔG < 0

Question 26

half-life

Answer 26

The time taken for the concentration of a reactant to decrease by half

Question 27

heterogeneous equilibrium

Answer 27

an equilibrium in which the species making up the reactants and products have different physical states

Question 28

homogeneous equilibrium

Answer 28

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

Question 29

hydrolysis

Answer 29

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

Question 30

initial rate of reaction

Answer 30

the change in concentration of a reactant or product per unit time at the start of the reaction: t = 0

Question 31

ionic product of water Kᵥᵥ

Answer 31

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

Question 32

lattice enthalpy

Answer 32

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

Question 33

ligand

Answer 33

A molecule or ion that can donate a pair of electrons to the transition metal ion

Question 34

ligand substitution

Answer 34

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

Question 35

mobile phase

Answer 35

The phase that moves in chromatography

Question 36

optical isomers

Answer 36

Stereosiomers that are non-superimosaable mirror images of each other (aka enantiomers)

Question 37

order

Answer 37

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

Question 38

overall order

Answer 38

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

Question 39

pH

Answer 39

The expression pH = -log[H⁺(aq)]

Question 40

precipitation reaction

Answer 40

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

Question 41

rate constant (k)

Answer 41

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 42

rate equation

Answer 42

For reaction: A + B -> C, - order m for A, n for B Rate equation= k[A]ᵐ[B]ⁿ

Question 43

rate determining step

Answer 43

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

Question 44

retention time

Answer 44

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

Question 45

Rf value

Answer 45

Rf = distance moved by component / distance moved by solvent

Question 46

second electron affinity

Answer 46

The enthalpy change that takes place when one electron is added to each ion in one mole of gaseous 1- ions to form one mole of gaseous 2- ions

Question 47

second ionisation energy

Answer 47

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 48

spin-spin coupling

Answer 48

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

Question 49

standard conditions

Answer 49

Pressure: 100 kPa Temperature: 298 K (25ºC) Concentration: 1 mol dm-3

Question 50

standard electrode potential

Answer 50

The e.m.f. of a half-cell compared with a standard hydrogen half-cell measured at 298 K with a solution concentrations of 1 mol dm-3 and a gas pressure of 100 kPa

Question 51

standard enthalpy change of atomisation

Answer 51

The enthalpy change that takes place when one mole of gaseous atoms forms from the element in its standard state.

Question 52

standard enthalpy change of formation ΔfH°

Answer 52

The enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states under standard conditions

Question 53

standard enthalpy change of hydration

Answer 53

The enthalpy change that takes place when one mole of isolated gaseous ions is dissolved in water forming one mole of aq ions under standard conditions

Question 54

standard enthalpy change of solution

Answer 54

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

Question 55

stationary phase

Answer 55

The phrase that doesn't move in chromatography

Question 56

transition element

Answer 56

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