Enthalpy definitions

Question 1

Standard molar enthalpy of formation

Answer 1

The enthalpy change when one mole of a compound is formed from its constituent elements under standard conditions, all reactants and products in their standard states

Question 2

Standard enthalpy of atomisation

Answer 2

the enthalpy change which accompanies the formation of one mole of gaseous atoms from the element under its standard state conditions

Question 3

First Ionisation

Answer 3

Standard enthalpy change when one mole of gaseous atoms is concerted into a mole of gaseous ions each with a single positive charge

Question 4

Second ionisation

Answer 4

Standard enthalpy change when one mole of electrons is lost from a mole of singly charged positive ions

Question 5

First electron affinity

Answer 5

Standard enthalpy change when a mole of gaseous atoms is converted to a mole of gaseous ions, each with a single negative charge

Question 6

Second Electron Affinity

Answer 6

Standard enthalpy change when one mole of electrons is added to a mole of gaseous ions each with a single charge to form ions each with two negative charges

Question 7

Lattice Enthalpy

Answer 7

Standard enthalpy change when one mole of solid ionic compound is formed from its gaseous ions

Question 8

Enthalpy of hydration

Answer 8

Standard enthalpy change when water molecules surround one mole of gaseous ions.

Question 9

Enthalpy of solution

Answer 9

Standard enthalpy change when one mole of solute dissolves completely in sufficient solvent to form a solution in which the molecules or ions are far apart enough not to interact with each other

Question 10

Which enthalpy changes are exothermic ?

Answer 10

Standard molar enthalpy of formation, First Electron Affinity, Lattice Enthalpy

Question 11

Which Enthalpy changes are endothermic ?

Answer 11

Standard enthalpy of atomisation, First ionisation, Second Ionisation, Second Electron Affinity, Lattice dissociation.

Question 12

What is endothermic and what direction are the arrows pointing in the Born-haber cycles?

Answer 12

Breaking bond, energy is needed to break the bonds. The arrow points upwards

Question 13

What is exothermic and what direction are the arrows pointing in the Born-haber cycles?

Answer 13

Exothermic is making bonds. Energy is released. The arrows face down

Question 14

In a Born-haber, which direction does the arrow point for Enthalpy of hydration?

Answer 14

Always from Gas to Aqueous solution

Question 15

In a Born-haber, which direction does the arrow point for Enthalpy of solution ?

Answer 15

From solid to Aqueous Solution

Question 16

What principle do you use for the Born-habor cycle?

Answer 16

The sum of clockwise = the sum of anti-clockwise

Question 17

How many times would you have to atomise Cl2(g)

Answer 17

Twice

Question 18

How many times would you have to atomise 3/2 O2?

Answer 18

2x3/2= 3

3 atomisations