Thermodynamics

Question 1

On a born- Hager cycle which way is exothermic

Answer 1

Down page

Question 2

On born-haber cycle which way is endothermic

Answer 2

Up page

Question 3

On born hacker cycle which way is up

Answer 3

Endothermic

Question 4

On born-Hager cycle which way is down

Answer 4

Exothermic

Question 5

What is the equation for Enthalpy of formation

Answer 5

Enthalpy of formation = sum of everything else

Question 6

How does lattice Enthalpy change down a group

Answer 6

Gets less negative

Question 7

How does size of ion affect lattice formation

Answer 7

The larger the ion, the less negative the eight alloy of lattice formation

Question 8

Why do larger ions have a less negative Enthalpy of lattice formation

Answer 8

Charges of larger ions are further apart, so weaker electrostatic force of attraction between them

Question 9

How does a bigger ionic charge affect Enthalpy

Answer 9

More negative, stronger Enthalpy

Question 10

What is the perfect ionic model used for

Answer 10

Predicting theoretical lattice enthalpies

Question 11

What are the assumptions for the perfect ionic model

Answer 11

• ions are 100% ionic
• ions are spherical
• attractions are purely electrostatic

Question 12

Why are there some discrepancies between experimental and theoretical values of lattice formation

Answer 12

The bond has some covalent character

Question 13

Which is bigger, born Haber value or theoretical value of lattice formation

Answer 13

Born haver value&raquo_space; theoretical value

Question 14

When do ions have a tendency towards covalent character

Answer 14

• +ve ion is small and has multiple charges
• -ve ions is larger and has multiple charges

Question 15

What is a spontaneous process

Answer 15

Will proceed on its own without any external influence

Question 16

Define entropy

Answer 16

The concept of increasing disorder

Question 17

What determines whether a reaction is feasible

Answer 17

The balance between entropy and Enthalpy

Question 18

What is the reaction for Gibbs’s free energy

Answer 18

G = H -T(S)

Question 19

What is the equation for entropy S

Answer 19

Sum S (products) - Sum S (reactants)

Question 20

What is the unit for entropy

Answer 20

J mol^-1 K^-1

Question 21

What must delta G be for a reaction to be feasible

Answer 21

Negative or 0

Question 22

What is delta G for physical state changes

Answer 22

Zero due to equilibria

Question 23

Define Enthalpy of solution

Answer 23

The standard Enthalpy change when 1 mole of an ionic solid dissolves in a large enough amount of water that the dissolved ions are well separated and do not interact with each other

Question 24

Define Enthalpy change of hydration

Answer 24

The Enthalpy change when one mole of gaseous ions becomes aqueous ions

Question 25

Is enthalpy of hydration reaction endo or exothermic

Answer 25

Exothermic reaction as bonds are made between ions are water molecules

Question 26

Why are ions attracted to water molecules

Answer 26

- +ve ions are attracted to s+ hydrogen on polar water molecules - -ve ions are attracted to s- oxygen on polar water molecules

Question 27

What is the relationship between charge density and hydration Enthalpy

Answer 27

The higher the charge density, the greater the hydration enthalpy

Question 28

When is a substance more likely to be soluble

Answer 28

If Hsol is exothermic

Question 29

When is a substance insoluble

Answer 29

If lattice enthalpy >> hydration , so Hsol is exothermic

Question 30

Define Enthalpy of formation

Answer 30

When 1 mole of a compound is formed from its constituent elements under standard conditions, 100KPa and 273K, with all reactants and products being in their standard states

Question 31

Define enthalpy if atomisation

Answer 31

Enthalpy change when 1 mole of gaseous atoms is formed for the element in its standard state

Question 32

Define bond dissociation enthalpy

Answer 32

The standard molar Enthalpy change when 1 mole of covalent bond is broken into two gaseous atoms