Physical A2 definitions

Question 1

Second ionisation energy

Answer 1

Enthalpy change when one mole of electrons are removed from one mole of gaseous +1 ions to form one mole of gaseous +2 ions under standard conditions.

Question 2

First ionisation energy

Answer 2

Enthalpy change when one mole of electrons are removed from one mole of gaseous atoms to form one mole of gaseous +1 ions under standard conditions.

Question 3

First electron affinity

Answer 3

Enthalpy change when one mole of electrons are added to one mole of gaseous atoms to form one mole of gaseous ions with a 1- charge under standard conditions.

Question 4

Second electron affinity

Answer 4

Enthalpy change when one mole of electrons are added to one mole of gaseous 1- ions to form one mole of gaseous ions with a 2- charge under standard conditions.

Question 5

Lattice enthalpy of dissociation

Answer 5

Enthalpy change when one mole of solid ionic compound dissociates into its gaseous ions under standard conditions.

Question 6

Lattice enthalpy of formation

Answer 6

Enthalpy change when one mole of solid ionic compound is formed from its gaseous ions, under standard conditions.

Question 7

Enthalpy of hydration

Answer 7

Enthalpy change when water molecules surround one mole of gaseous ions, under standard conditions

Question 8

Enthalpy of solution

Answer 8

Enthalpy change when one mole of solute dissolves completely in sufficient solvent to form a solution in which the molecules or ions are far enough apart to not interact with each other, under standard conditions.

Question 9

Mean bond enthalpy

Answer 9

Enthalpy change required to break one mole of a covalent bond under standard conditions averaged over a range of compounds.

Question 10

Entropy

Answer 10

Mathematical measure of how random a system is. The more disordered something is, the greater the entropy. (Units Kmol-1K-1)

Question 11

Order of reaction

Answer 11

The order of reaction is defined as the power dependence of the rate on the concentration of each reactant.

Question 12

Rate constant

Answer 12

Is the proportionality constant relating the rate of the reaction to the concentrations of reactants

Question 13

Brønsted–Lowry acid

Answer 13

A substance that donates a proton (H+)

Question 14

Brønsted–Lowry base

Answer 14

A substance that can accept a proton.

Question 15

Strong acids

Answer 15

Acids that fully dissociate into H+ in solution. E.g. HCl, H2SO4, HNO3

Question 15

Brønsted–Lowry acid-base reaction

Answer 15

Reaction involving the transfer of a proton.

Question 16

Weak acid

Answer 16

An acid that partially dissociated into H+ in solution but most of the acid remains undissociated. E.g. carboxylic acids

Question 17

Buffer

Answer 17

A solution that resists change in pH when small amounts of acid/alkali are added.

Question 18

Acidic buffer

Answer 18

Contain a weak acid and the salt of that weak acid

Question 19

Basic buffer

Answer 19

Contain a weak base and the salt of that weak base.

Question 20

Equivalence point

Answer 20

Volume where you have exactly the same number of moles of H+ ions and OH- ions.

Question 21

End point

Answer 21

The volume of alkali or acid added where the indicator just changes colour.

Question 22

Half cell

Answer 22

A piece of metal dipped into a solution of its own ions.

Question 23

Salt bridge

Answer 23

Filter paper soaked in KNO3 which allows ions to flow through the circuit balancing charges and completing the circuit.

Question 24

Electrochemical series

Answer 24

List of electrode potentials in numerical order.