Definitions

Question 1

Enthalpy change of reaction

Answer 1

The energy change associated with a given reaction

Question 2

Enthalpy change of formation

Answer 2

The energy change that takes place when 1 mole of a compound is formed from its constituent elements in their standard conditions
Exotherminc process

Question 3

Enthalpy change of combustion

Answer 3

The energy change that takes place when one mole of a substance is completely combusted

Question 4

Enthalpy change of neutralisation

Answer 4

The energy change that takes is associated with the formation of 1 mole of water from a neutralisation reaction

Question 5

Standard enthalpy change of atomisation

Answer 5

The energy change that takes place when one mole of gaseous atoms is formed from its element in its standard state
Endothermic process

Question 6

First ionisation energy

Answer 6

The energy required to remove one electron from each atom in one mole of the gaseous element to form one mole of gaseous 1+ ions
Endothermic process

Question 7

First electron affinity

Answer 7

The energy required to add electrons to atoms to form one mole of gaseous 1- ions from gaseous atoms
Exothermic process because electron is attracted into the outer shell of an atom by the nucleus

Question 8

Second electron affinity

Answer 8

The energy required to add electrons to form one mole of gaseous 2- ions from gaseous 1- ions
Endothermic process because the electron is repelled by the 1- ion and this repulsion has to be overcome

Question 9

Relative isotopic mass

Answer 9

The mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon 12

Question 10

Relative atomic mass

Answer 10

The weighted mean mass of an atom of an element compared with one twelfth the mass of an atom of carbon 12

Question 11

A mole

Answer 11

The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon 12 isotope

Question 12

Activation energy

Answer 12

The minimum energy required to start a reaction by breaking bonds in the reactants

Question 13

Amphoteric substances

Answer 13

substances that can react as both acids and bases e.g amino acids

Question 14

Atomic orbital

Answer 14

A region of space where it is likely you will find electrons. Each orbital can hold up to 2 electrons with opposite spins.

Question 15

Average bond enthalpy

Answer 15

The mean energy needed for 1 mole of a given type of gaseous bonds to undergo homolytic fission.

Question 16

cis-trans isomerism

Answer 16

a type of E/Z isomerism where two substituent groups attached to each carbon atom of the C=C is the same

Question 17

Covalent bond

Answer 17

A bond formed by a shared pair of electrons between nuclei

Question 18

Dative covalent bond

Answer 18

A bond formed by a shared pair of electrons that has been provided by one of the bonding atoms only.

Question 19

Displayed formula

Answer 19

A formula which shows the relative positioning of atoms and the bonds between them.

Question 20

Disproportionation

Answer 20

The oxidation and reduction of the same element in a redox reaction

Question 21

E/Z isomerism

Answer 21

A type of stereoisomerism that is caused by the restricted rotation around the double bond, two different groups are attached to each carbon atom of the C=C double bond.

Question 22

Electron shielding

Answer 22

The repulsion between electrons in different inner shells. Shielding reduces the net attractive force from the positive nucleus on the outer electrons.

Question 23

Electrophile

Answer 23

An electron pair acceptor

Question 24

Empirical formula

Answer 24

The simplest whole number ratio of atoms of each element present in a compound.

Question 25

Endothermic

Answer 25

A reaction in which the enthalpy change is positive, the enthalpy of the products is greater than that of the reactants. This results in heat being taken in from the surroundings.

Question 26

Exothermic

Answer 26

A reaction in which the enthalpy change is negative, the enthalpy of the products is smaller than that of the reactants. Heat is lost to the surroundings (temperature increases)

Question 27

Heterogeneous catalyst

Answer 27

A catalyst used in a reaction which is in a different phase from the reactant.

Question 28

Heterolytic fission

Answer 28

When one bonding atom receives both electrons from the bonding pair.

Question 29

Homolytic fission

Answer 29

When each bonding atom receives one electron from the bonded pair, forming two radicals.

Question 30

Homogeneous catalyst

Answer 30

A catalyst used in a reaction that is in the same phase as the reactant

Question 31

Ionic bond

Answer 31

The electrostatic attraction between oppositely charged ions

Question 32

Isotopes

Answer 32

Atoms of the same element with different numbers of neutrons (same atomic number different mass number)

Question 33

Le Chatelier's principle

Answer 33

When a system in dynamic equilibrium is subjected to change, the equilibrium will shift to minimise the change.

Question 34

London forces

Answer 34

Attractive forces between induced dipoles in neighbouring molecules

Question 35

Lone pair

Answer 35

An outer shell pair of electrons that is not involved in chemical bonding

Question 36

Metallic bonding

Answer 36

The electrostatic attraction between positive metal ions and delocalised electrons

Question 37

Nucleophile

Answer 37

An electron pair donor

Question 38

Permanent dipole

Answer 38

A small charge difference across a bond that results from a difference in electronegativity of the bonded atoms.

Question 39

Permanent dipole-dipole interaction

Answer 39

A weak attractive force between permanent dipoles and permanent dipoles or induced dipoles in neighbouring polar molecules.

Question 40

pi bonds

Answer 40

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

Question 41

Radical

Answer 41

A highly reactive species with one or more unpaired electrons

Question 42

Rate of reaction

Answer 42

The change in concentration of a reactant or a product in a given time

Question 43

Salt

Answer 43

A chemical compound formed from an acid when an H+ ion from the acid has been replaced by a metal or another positive ion

Question 44

Sigma bonds

Answer 44

Made by the direct overlap between orbitals on the bonding atoms

Question 45

Specific heat capacity

Answer 45

The energy required to raise 1g of a substance by 1K

Question 46

Stereoisomers

Answer 46

Organic compounds with the same molecular and structural formulae but have different arrangements of atoms in space.

Question 47

Structural formula

Answer 47

Provides minimal detail to show the arrangement of atoms in a molecule

Question 48

Structural isomers

Answer 48

Compounds with the same molecular formula but different structural formula

Question 49

Water of crystallisation

Answer 49

Water molecules that form an essential part of the crystalline strutcure of a compound