A2 2 Definitions

Question 1

Standard Enthalpy of formation

Answer 1

The Enthalpy change when 1 mole of a substance is formed from its elements, in their natural state, under standard conditions

Question 2

Standard Enthalpy of atomisation

Answer 2

The Enthalpy change when 1 mole of gaseous atoms is formed from its elements in its standard state

Question 3

1st ionisation energy

Answer 3

The energy required to remove 1 electron from each atom in one mole of gaseous atoms, to form one mole of gaseous 1+ ions

Question 4

2nd ionisation energy

Answer 4

The energy required to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

Question 5

1st electron affinity

Answer 5

The energy required to form one mole of negatively charged ions from one mole of atoms, in the gaseous state

Question 6

2nd electron affinity

Answer 6

The energy required to form 1 mole of 2- ions from one mole of 1- ions, in the gaseous state

Question 7

Hess’ Law

Answer 7

The Enthalpy change for a reaction is the same,irrespective of the route taken, provided the initial and final conditions are the same

Question 8

Standard Enthalpy of solution

Answer 8

Enthalpy change when one mole of a compound is completely dissolved in water, under standard conditions

Question 9

Standard Enthalpy of hydration

Answer 9

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

Question 10

Entropy

Answer 10

A measure of disorder in a system (S)

Question 11

Standard electrode potential

Answer 11

The voltage of a half cell, compared to a standard hydrogen half cell, measured at 298K, with solution concentrations of 1moldm-3 and a gas pressure of 1atm

Question 12

Standard Lattice Enthalpy

Answer 12

The Enthalpy change when one mole of a solid ionic lattice is formed, from its gaseous ions under standard conditions. Always exothermic

Question 13

Transition element

Answer 13

A d block element, that forms an ion with an incomplete d sub shell

Question 14

Catalyst

Answer 14

Increases the rate of reaction, without being used up. Provides an alternative route, with lower activation energy

Question 15

Ligand

Answer 15

A molecule or ion which possesses at least one lone pair of electrons, which can be donated into vacant d orbitals of a metal ion, by forming a co-ordinate bond

Question 16

Co-ordination number

Answer 16

The total number of co-ordinate bonds formed between a central metal ion and it’s ligands

Question 17

Bidentate ligand

Answer 17

Can donate two lone pairs of electrons into the vacant d orbitals of a metal ion, forming two co-ordinate bonds

Question 18

Dynamic equilibrium

Answer 18

Reached in a closed system where:

• rate of forward reaction equals the rate of the reverse reaction
• the concentrations of the reactants and products remain the same but are constantly interchanging

Question 19

Le Chatelier’s principle

Answer 19

When a system in equilibrium is subjected to a change, the position of equilibrium will shift to minimise that change

Question 20

Bronstead Lowry theory

Answer 20

Acid: proton donor
Base: proton acceptor

Question 21

Buffer

Answer 21

Minimises changes in pH, on addition of small amounts of acid or base

Question 22

Titration end point

Answer 22

The stage where the indicator used has a colour halfway between it’s extreme colours

Question 23

Equivalence point

Answer 23

The point of neutralisation - when an acid and a base have completely reacted

Question 24

Standard Enthalpy change of Neutralisation

Answer 24

The energy change when an aqueous acid is neutralised by an aqueous base, to form one mole of water, under standard conditions

Question 25

Oxidation state

Answer 25

State which a metal achieves as a result of losing electrons

Question 26

Precipitation reaction

Answer 26

A reaction in which soluble ions, in separate solutions, are mixed together to produce an insoluble compound or precipitate

Question 27

Order

Answer 27

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

Question 28

Rate determining step

Answer 28

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

Question 29

Rate

Answer 29

Change in concentration of a reactant or product with time

Question 30

Initial Rate

Answer 30

The rate at the start of a reaction, when t=0