Enthalpy and Entropy Word Stimulants

Question 1

Lattice Enthalpy

Answer 1

Measure of ionic strength in giant ionic lattice

Exothermic (formation of bonds) H -

Question 2

Lattice Enthalpy* Definition

Answer 2

Enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions.

Question 3

Born - Harber Cycle

Answer 3

Left: Formation (down arrow) ; elements standard states; Atomisation ^; gaseous atoms; first ionisation energy ^
Right: Electron affinity (down arrow); gasous ions; lattice enthalpy change (down arrow)
Bottom : ionic lattice

Question 4

Enthalpy Change of Formation*

Answer 4

Enthalpy change for the formation of 1 mol of a compound from its elements in their standard states under standard conditions.

Question 5

Enthalpy change of atomisation

Answer 5

Formation of 1 mol of gaseous atoms from the electrons in SS under SC.

Question 6

First ionisation energy*

Answer 6

Enthalpy change for the removal of 1 e- from each arom in 1 mol of gaseous atoms to form 1 mol of gaseous 1+ ions.

Question 7

First electron affinity

Answer 7

Addition of 1 e- to each atom in 1 mol of gaseous atoms to form 1- ions.

Question 8

Enthalpy change in solution

Answer 8

Dissolve ionic compound in H2O

Ionic lattic breaks up -> gaseous ions -> bond to h2o -> aq ions

Question 9

Lattice enthalpy in solution

Answer 9

Energy to break ionic bonds
Formation : endothermic
Breaking : exothermic

Question 10

Enthalpy Change of hydration

Answer 10

Enthalpy change when one mole of gaseous ions dissolve in water to form aqueous ions
g + aq -> aq
Exothermic

Question 11

Enthalpy change of solution

Answer 11

Enthalpy change when one mole of a solute dissolves in a solvent
Exothermic or endothermic

Question 12

Born-Harber Soltution

Answer 12

Top: Gaseous ions
Bottom: Ionic Lattice
Left : Lattice Enthalpy
Right: Hydration (down arrows); aq ions; Solution ^ (at bottom)

Question 13

Factors affecting lattice enthalpy

Answer 13

Ionic size

ionic charge

Question 14

Ionic size increase

Answer 14

Attraction between oppositiely charge ions decrease - ionic radius +
Lattice enthalpy change - less exothermic
Melting point decrease - less energy to overcome decreased attraction

Question 15

Ionic charge increase

Answer 15

Attraction between oppositiely charge ions increase
Lattice enthalpy change - more exothermic
Melting point increased - more energy to overcome increased attraction

Question 16

Factors affecting Hydration enthalpy

Answer 16

Ionic size
Ionic charge
Ionic size decrease, ionic charge increase
Attraction between ions and h20 +
Enthalpy change of hydration more exothermic

Question 17

Entropy

Answer 17

S

Measure of the dispersal of energy in a system

Question 18

Greater Entropy

Answer 18

Greater dispersal, greater disorder

More positive

Question 19

Standard Entropy Change

Answer 19

Entropy content of 1 mol of a substance under standard conditions
KJ-1mol-1
Always positive

Question 20

Solid > Liquid > Gas

Answer 20

Particals more random

S increases , more +

Question 21

Gaseous moles

Answer 21

Increase in gaseous molecules = increase entropy

Decrease in gaseous molecules = decrease entropy

Question 22

S calculation

Answer 22

(Sum of) S products - (Sum of) S reactants

Question 23

Free Energy Change

Answer 23

G

Overall energy change of reaction

Question 24

Feasible

Answer 24

Products lower energy than reactants
G<0 (negative G)
H-TS<0

Question 25

G Calculation

Answer 25

G = H - TS
(kJmol-1)
Enthalpy change (kJ mol-1)
Temp (K)
Entropy change of system (JK-1mol-1) divide by 1000

Question 26

Temperature increase effect on G

Answer 26

TS more significant
May outweigh H
Not feasible

Question 27

Limitations of free energy

Answer 27

G not take into account rate (slow)