A Level Physical

Question 1

Enthalpy of formation

Answer 1

Enthalpy change when one mole of a substance is formed from its constituent elements with all substances in their standard state.

Question 2

Enthalpy of combustion

Answer 2

Enthalpy change when one mole of a substance undergoes complete combustion in oxygen with substances in standard state.

Question 3

Enthalpy of neutralisation

Answer 3

Enthalpy change when one mole of water is formed in a reaction between an acid and alkali under standard conditions.

Question 4

First ionisation energy

Answer 4

Enthalpy change when each atom in one mole of gaseous atoms loses one electron to form one mole of gaseous 1+ ions.

Question 5

Second ionisation energy

Answer 5

Enthalpy change when each atom in one mole of gaseous 1+ ions loses one electron to form one mole of gaseous 2+ ions.

Question 6

First electron affinity

Answer 6

Enthalpy change when each atom in one mole of gaseous atoms gains one electron to form one mole of gaseous 1- ions.

Question 7

Second electron affinity

Answer 7

Enthalpy change when each atom in one mole of gaseous 1- ions gains one electron to form one mole of gaseous 2- ions.

Question 8

Enthalpy of atomisation

Answer 8

Enthalpy change when one mole of gaseous atoms is produced from an element in its standard state.

Question 9

Hydration enthalpy

Answer 9

Enthalpy change when one mole of gaseous ions become hydrated (dissolved in water).

Question 10

Enthalpy of solution

Answer 10

Enthalpy change when one mole of an ionic solid dissolves in an amount of water large enough so that the dissolved ions are well separated and do not interact with each other.

Question 11

Bond dissociation enthalpy

Answer 11

Enthalpy change when one mole of covalent bonds is broken in the gaseous state.

Question 12

Lattice enthalpy of formation

Answer 12

Enthalpy change when one mole of a solid ionic compound is formed from its constituent ions in the gas phase.

Question 13

Lattice enthalpy of dissociation

Answer 13

Enthalpy change when one mole of a solid ionic compound is broken up into its constituents ions in the gas phase.

Question 14

Enthalpy of vaporisation

Answer 14

Enthalpy change when one mole of a solid is turned into a gas.

Question 15

Enthalpy of fusion

Answer 15

Enthalpy change when one mole of a solid is turned into a liquid.

Question 16

Born Haber cycles

Answer 16

Draw them!

Question 17

Trends in lattice enthalpies

Answer 17

Strength of enthalpy of lattice formation depends on:
-Size of ions (larger ions, less negative enthalpies).
-Charge of ion (bigger charge, greater attraction).

Question 18

Perfect ionic model

Answer 18

Theoretical lattice enthalpies assume a perfect ionic model where ions are 100% ionic and spherical and attractions are purely electrostatic.

Question 19

Differences between theoretical and Born Haber (experimental) lattice enthalpies

Answer 19

-Born Haber is the real experimental value.
-Differ due to covalent character.
-The more the covalent character, the bigger the difference in values.

Question 20

Tendency in covalent character due to:

Answer 20

-Positive ion is small
-Positive ion has multiple charges
-Negative ion is large
-Negative ion has multiple negative charges.

Question 21

Positive ions with covalent character

Answer 21

-Small, highly charged and very good at distorting.
-Very good at polarising negative ions.

Question 22

Negative ions with covalent character

Answer 22

-Large, highly charged and easier to distort.
-Very polarisable.

Question 23

Why does one compound form over the other?

Answer 23

The most exothermic enthalpy of formation is the one that forms as it is the most thermodynamically stable.

Question 24

Spontaneous process

Answer 24

It will proceed on its own without any external influence.

Question 25

Entropy