Enthalpy And Entropy

Question 1

Define lattice enthalpy

Answer 1

Enthalpy change when 1 mol of an ionic compound is formed from its gaseous ions under standard conditions

Question 2

What is lattice enthalpy

Answer 2

The energy needed to form ionic bonds

Question 3

Is lattice enthalpy endothermic or exothermic

Answer 3

Exothermic because bonds are formed

Question 4

Define the standard enthalpy change of formation

Answer 4

Enthalpy change when 1 mol of a compound is formed from its constituent elements under standard conditions

Question 5

Define standard enthalpy change of atomisation

Answer 5

Enthalpy change when 1 mol of gaseous atoms form from its constituent elements under standard conditions

Question 6

Is the enthalpy change of atomisation endothermic or exothermic

Answer 6

Endothermic because bonds are broken

Question 7

Define first ionisation energy

Answer 7

Enthalpy change when 1 electron is removed form each atom in one mol of gaseous atoms to form 1 mol of gaseous 1+ ions

Question 8

Are first ionisation energies exothermic or endothermic

Answer 8

Endo because energy needed to overcome attraction of electron to nucleus

Question 9

Define standard electron affinity

Answer 9

Enthalpy change when an electron is added to each atom in 1 mol of gaseous atoms to form 1 mol of gaseous 1- ions

Question 10

Are standard electron affinities endothermic or exothermic

Answer 10

Exothermic

Energy released when electron is attracted to the nucleus

Question 11

Are successive electron affinities endothermic or exothermic

Answer 11

Always endothermic

Energy needed to overcome repulsive force os negetive ion

Question 12

How do you indirectly fing the lattice enthalpy

Answer 12

Using born haber cycles

Question 13

Define the enthalpy change of solution

Answer 13

Enthalpy change when 1 mol of solute dissolves in solvent

Water overcomes ionic bonds

Question 14

Define the enthalpy change of hydration

Answer 14

Enthalpy change when 1 mol of gaseous atoms are dissolved to form 1 mol of aqueous ions

Question 15

What stages does dissolving involve

Answer 15

Breaking of ionic bonds to form gaseous ions

Dissolving of gaseous ions to produce aqueous ions

Question 16

What does the negetive of the lattice enthalpy mean

Answer 16

The energy needed to break the ionic lattice

Question 17

What factors affect lattice enthalpy

Answer 17

Ionic radius and charge

Question 18

How does ionic radius affect lattice enthalpy

Answer 18

Smaller radius = stronger attraction between ions = more negetive enthalpy

Larger charge density

Question 19

How does ionic charge affect lattice enthalpy

Answer 19

Larger charge = stronger attraction between ions = more negetive enthalpy

Larger charge density

Question 20

Why can lattice enthalpy be used to predict melting point

Answer 20

More negetive lattice enthalpy stronger bonds= higher melting point

Question 21

Factors affecting enthalpy of hydration

Answer 21

Ionic radius and charge

Question 22

How does ionic radius affect enthalpy of hydration

Answer 22

Large radius= less attraction between ions and water

Hydration enthalpy is less negetive

Question 23

How does the ionic charge affect enthalpy of hydration

Answer 23

Larger charge = Larger attraction between ions and water

More negetive enthalpy

Question 24

How can you predict solubility

Answer 24

More negetive enthalpy of solution = more likely to Dissolve

Question 25

Define Entropy

Answer 25

Increase in disorder

Question 26

Order the states form least to most Entropy

Answer 26

Solid liquid gas

Question 27

What is the value for Entropy at oK

Answer 27

O

Question 28

What does negetive and positive Entropy change mean

Answer 28

Negetive = more ordered Positive = less ordered more random

Question 29

What is the sign for the Entropy change from solid to liquid

Answer 29

Positive

Question 30

Define Entropy change

Answer 30

Entropy one one mole of a substance under standard conditions

Question 31

How is Entropy change calculated

Answer 31

Entropy of products - Entropy of reactants

Question 32

What must the value of Entropy change be for a reaction to be feasible

Answer 32

>0

Question 33

Define feasibility

Answer 33

Whether a reaction is energetically possible/ spontaneous

Question 34

What is the value for gibbs free energy for a reaction to be feasible and just feasible

Answer 34

<0 =0

Question 35

Why might G<0 but not spontaneous

Answer 35

Large Ea so slow rate of reaction