3.1.8 Thermodynamics

Question 1

The standard molar enthalpy of formation

Answer 1

When one mol of a compound is formed from its elements at standard states at standard conditions.

Elements → compound

Question 2

The standard enthalpy of atomisation

Answer 2

The enthalpy change of one mol of gaseous atoms form the elements at standard states understandard conditions.

Atom → 1 mol of gaseous atom

Question 3

First ionisation energy

Answer 3

The standard enthalpy changes when 1 mol of gaseous atoms is converted to one mol of gaseous ions each with a single positive charge.

Metal atom → 1+ion

Question 4

Second ionisation energy

Answer 4

The loss of a mol of electrons from a mol of 1+ions

1+ion → 2+ion

Question 5

First electron affinity

Answer 5

When a mol of gaseous atoms is converted to a mol of gaseous 1- ions

Non metal atom → 1-ion

Question 6

Second electron affinity

Answer 6

When a mol of electrons is added to a mol of gaseous ions with a 1- charge

1-ion → 2-ion

Question 7

Lattice enthalpy of formation

Answer 7

When one mol of solid ionic compound is formed from its gaseous ions

Gaseous ions → ionic compound

When a lattice is formed energy is released. Separating requires energy.

Question 8

Trends in lattice enthalpy

Answer 8

Larger ion = smaller lattice enthalpy (as the opposite charges are further apart)
For ions of a similar radius it increases with the charge of the ion.

Question 9

Theoretical compound

Answer 9

Can predict lattice enthalpy of formation theoretically using born haber cycles.
Can you predict from the size of the metal ion and the structure of the crystals ???

Question 10

find the enthalpy change of hydration when an ionic solid is dissolved in water

Answer 10

Enthalpy change of Lattice of dissociation
Pos ions hydrated lattice enthalpy of hydration given out
Neg ions hydrated lattice enthalpy of hydration given out

Question 11

Lattice enthalpy of dissociation

Answer 11

The ionic lattice breaks to give separate gaseous ions.

ionic lattice → separate gaseous ions

Question 12

Difference between theoretical lattice enthalpy predictions

Answer 12

Polarisation when small highly charged negative ions disrupt large highly charged negative ions. Leading to a degree of covalent bonding. Causing a difference between theoretical values.

Question 13

Forces that make chemical reactions happen

Answer 13

Increase in entropy - increase in randomness delta S
Decrease in enthalpy - decrease in energy delta H

Question 14

What are feasible reactions favoured by

Answer 14

Positive entropy changes +delta s (products more random than reactants)
Negative enthalpy changes (energy given out)

Question 15

Gibbs free energy equation

Answer 15

delta G = delta H - T delta S
T = temperature

Question 16

Value of delatG where it is feasible

Answer 16

0
So can calculate the temperature at which the reaction becomes feasible

Question 17

born habour cycle calculation

Answer 17

arrow going oposite to direction = arrows going the correct direction

Question 18

delta H of solution

Answer 18

= delat H lattice dissociation - (delta H hydra cation + delat H of hydr of anion)

multiply the delta hydra by the nub of ion present for the anion or cation

Question 19

entropy at diffrent states

Answer 19

gas is more disordered than a solid

Question 20

when us teh standard entropy os a substance 0

Answer 20

at OK
as particals are stationary meaning no vibration
meaning no dissorder

Question 21

difference between boiling and melting

Answer 21

boiling has a bigger change in dissorder thena melting

Question 22

delta G =

Answer 22

AH -TAS

linear realtionship

Question 23

why delta G decreases as T increases

Answer 23

as Tdelta S gets bigger as the particals are moving more meaning ore dissorder

Question 24

frsible when …

Answer 24

delta G is negative

Question 25

how to calculate delat S from a table

Answer 25

products - reactants

Question 26

what happens at a standard state

Answer 26

entropy data is wrong

Question 27

reason the first elctron affinity of oxygen in an exothermic process

Answer 27

attractive force between the nucleas of atom and external electron

Question 28

dela solution of a compound =

Answer 28

A H lattce enthalpy of the compound