Energetics

Question 1

Lattice Enthalpy

Answer 1

Enthalpy change when one mole of an ionic compound is converted into gaseous ions

Question 2

Standard enthalpy of Atomisation

Answer 2

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

Question 3

Bond Dissociation Enthalpy

Answer 3

Energy required to break 1 mol of a covalent bond under standard conditions

Question 4

Trend of Lattice Enthalpy in metal ions

Answer 4

Decreases as ions get bigger
Distance between neighbouring ions increases down group

Question 5

Is lattice enthalpy of Group 2 oxide or Group 2 fluoride greater?
Why?

Answer 5

Group 2 Oxide

Charge on oxide ion greater than fluoride ion

Question 6

Trends in Lattice Enthalpy

Answer 6

Ion Charge Increase = LE Increase
Ion Size Decrease = LE Increase

Question 7

What enthalpy change cannot be experimented

Answer 7

Standard Lattice Enthalpy

Question 8

What is technique of applying Hess Law to standard enthalpy changes of formation ionic compund?

Answer 8

Born-Haber Cycle

Question 9

First Electron Affinity

Answer 9

Enthalpy change when 1mol of gaseous atoms is converted to gaseous ions with a single negative charge

Question 10

What is Bond Dissociation Enthalpy in Diatomic Elements

Answer 10

Twice the Standard Enthalpy of Atomisation

Question 11

Equation Of Born Haber

Answer 11

Latt+F=Everything else added together

Latt= everything added - F

Question 12

Born Haber Group 2 Halide
Clockwise

Answer 12

UP:
Formation (arrow down)
Atomisation Metal
IE1Metal
IE2 Metal
2xA Halide

Down:
EA1 Halide
Latt Compound (arrow up)

Question 13

What is diff in a Born Haber for oxides

Answer 13

There will be 2 EA for Oxygen

First Exothermic (-)
EA2 Endothermic (+) - repulsion between O- and e-

Question 14

Enthalpy Of Hydration

Answer 14

Enthalpy change when 1mol of gaseous ions is converted into 1mol of aqueous ions

Question 15

Enthalpy of Solution

Answer 15

Enthalpy change when 1mol of solute dissolves in water

Question 16

Equation for Enthalpy of Solution

Answer 16

Enthalpy solution = lattice enthalpy + enthalpy hydration

solH° = lattH° + hydH°

Question 17

What can you use for water in enthalpy equation

Answer 17

(aq)

Question 18

Halides of metals with oxidation state +2

Answer 18

2 times enthalpy hydration of halide req
2mol Halide in 1mol Ionic cmpnd

Question 19

What happens when ionic compounds dissolve in water

Answer 19

Delta- O in H2O attract positive ions

Delta+ H in H2O attracted to negative ions

(pg 13 for diagram)

Question 20

Values For Enthalpy Of Hydration

Answer 20

• exothermic - energy released when ions attracted to polar water form weak forces

•smaller ions w/ same charge = more negative - higher charge density attracts +H more

• smaller cations attracts -O more
-more negative