A level Definitions

Question 1

Relative Isotopic Mass

Answer 1

The mass of an atom of an isotope compared with 1/12th mass of carbon-12

Question 2

Relative Atomic Mass (Ar)

Answer 2

The weighted mean mass of an atom of an element compared with 1/12th mass of carbon-12

Question 3

Isotopes

Answer 3

Atoms of an element with the same number of protons but different number of neutrons.

Question 4

Molar Mass

Answer 4

Mass per mole units g mol^-1

Question 5

Mole

Answer 5

The amount of substance 1 mole is 6.02 x 10^23 particles

Question 6

Acid

Answer 6

Releases H+ ion aqueous solution

Question 7

Alkali

Answer 7

A soluble base that releases OH- ions in an aqueous solution.

Question 8

Strong Acid

Answer 8

Fully dissociates in solution

Question 9

Weak Acid

Answer 9

Partially dissociates in solution

Question 10

Orbital

Answer 10

A region around the nucleus that can hold up to two electrons, with opposite spins

Question 11

Disproportionation

Answer 11

Oxidation and reduction of the same element

Question 12

First Ionisation Energy

Answer 12

The energy needed to remove 1 mole of electrons from 1 mole gaseous of atoms to form one mole of gaseous 1+ ions.

Question 13

Ionic bonding

Answer 13

The electrostatic attraction between oppositely charged ions. (usually between a metal and non-metal)

Question 14

Covalent Bonding

Answer 14

Strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms ( 2 non-metals)

Question 15

Polar molecule

Answer 15

Compound has polar bonds with dipoles that do not cancel due to their direction

Question 16

Metallic bonding

Answer 16

The electrostatic attraction between positively charged metal ions and the sea of delocalised electrons.

Question 17

Electronegativity

Answer 17

the ability of an atom to attract the bonding electrons in a covalent bond

Question 18

Standard states

Answer 18

physical states under standard conditions

Question 19

Standard conditions

Answer 19

Temperature: 298 kelvin Pressure: 100 KPa

Question 20

Enthalpy change of formation

Answer 20

The enthalpy change when one mole of a compound is formed from its elements in their standard states

Question 21

Enthalpy change of combustion

Answer 21

The enthalpy change for the complete combustion of one mole of a substance

Question 22

Enthalpy change of neutralisation

Answer 22

The enthalpy change for the formation of 1 mol of water from a neutralisation reaction

Question 23

Activation energy

Answer 23

the minimum energy required for a reaction to take place

Question 24

Homologous Series

Answer 24

(a series of organic compounds having) the same functional group but with each successive member differing by CH2

Question 25

Structural isomers

Answer 25

Compounds with the same molecular formula but different structural formula

Question 26

Homolytic fission

Answer 26

Breaking a covalent bond to form two radicals

Question 27

Heterolytic fission

Answer 27

Breaking a covalent bond to form two oppositely charged ions

Question 28

E/Z isomerism

Answer 28

an example of stereoisomerism, due to restricted rotation about a double bond and two different groups attached to each carbon atom of the C=C group

Question 29

Cis-trans isomerism

Answer 29

A special case of E/Z isomerism in which two of the substituent groups attached to each carbon atom of the C=C group are the same

Question 30

Electrophile

Answer 30

An electron pair acceptor

Question 31

Nucleophile

Answer 31

An electron pair donor

Question 32

Homogeneous catalyst

Answer 32

A catalyst in the same state as the reactants (usually in solutions)

Question 33

Heterogeneous catalyst

Answer 33

- A catalyst in a different state to the reactants (usually a solid catalyst with reactants in solution or gas)

Question 34

Dynamic equilibrium

Answer 34

When the rate of the forward reaction is equal to the rate of the reverse reaction and the concentrations of reactants and products do not change in a closed system

Question 35

Catalyst

Answer 35

Chemical that increases the rate of both forward and reverse reactions in an equilibrium by the same amount resulting in an unchanged position of equilibrium

Question 36

σ-bond

Answer 36

Overlap of orbitals directly between the bonding atoms

Question 37

π-bond

Answer 37

Sideways overlap of adjacent p-orbitals above and below the bonding C atoms

Question 38

Stereoisomerism

Answer 38

Compounds with the same structural formula but a different arrangement of atoms in space

Question 39

Curly arrow

Answer 39

Shows the movement of an electron pair during a reaction

Question 40

Rate of reaction

Answer 40

the rate at which the concentration of a reactant or product is formed/used

Question 41

Half-life

Answer 41

The time taken for the concentration of a reactant to half

Question 42

Rate-determining step

Answer 42

the slowest step in a multistep reaction

Question 43

Brønsted-Lowry acid

Answer 43

a species that donates a proton (H+)

Question 44

Brønsted-Lowry base

Answer 44

a species that accepts a proton (H+)

Question 45

Buffer solution

Answer 45

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

Question 46

Lattice Enthalpy

Answer 46

enthalpy change for the formation of 1 mole of ionic lattice from gaseous ions, ΔLEH

Question 47

Enthalpy change of solution

Answer 47

enthalpy change for dissolving of 1 mol of solute, ΔsolH

Question 48

Enthalpy change of hydration

Answer 48

enthalpy change for dissolving of 1 mol of gaseous ions in water, ΔhydH

Question 49

Oxidising agent

Answer 49

the chemical that is reduced and oxidises another species

Question 50

Reducing agent

Answer 50

the chemical that is oxidised and reduces another species

Question 51

Standard electrode (redox) potential, Eo

Answer 51

the voltage produced when a half cell is connected to a standard hydrogen half-cell, measured at 298K with solution concentrations of 1 mol dm^-3 and a gas pressure of 100KPa.

Question 52

Ligand

Answer 52

species that donates a pair of electrons forming a coordinate/dative covalent bond to a metal ion

Question 53

Optical isomer

Answer 53

non-superimposable mirror images about a chiral centre