Lattice Enthalpy

Question 1

Why is lattice enthalpy always endothermic?

Answer 1

Because the process is bond breaking.

Question 2

What does the strength of an ionic lattice depend on?

Answer 2

Depends on the strength of the force of attraction between ions.

Question 3

How does Ionic charge effect lattice enthalpy?

Answer 3

The greater the charge on one/both ions the stronger the attractive forces which require more energy to break. Bond breaking is an endothermic process. This means 1+/- ions form compounds with lower lattice enthalpies than 2+/- ions.

Question 4

How does ionic radii effect lattice enthalpy?

Answer 4

The larger the ionic radius, the lower the lattice enthalpy. This is because the packing of the ions is less efficient and there is less interaction between them. Therefore, a group 2 ion will have a lower lattice enthalpy than a group 7 ion.

Question 5

Arrows up

Answer 5

Endothermic

Question 6

Arrows down

Answer 6

Exothermic

Question 7

Enthalpy of formation

Answer 7

exothermic

Question 8

Enthalpy of atomisation of metal

Answer 8

endothermic

Question 9

Ionisation energy of metal

Answer 9

endothermic

Question 10

Enthalpy of atomisation of non-metal

Answer 10

endothermic

Question 11

Electron affinity of non-metal

Answer 11

1st exothermic, 2nd endothermic

Question 12

lattice energy of ionic compound

Answer 12

endothermic

Question 13

Atomisation of metal down group.

Answer 13

Strength of metallic bonds decreases down group as atomic radius increases therefore atomisation becomes less endothermic (less attraction to break bonds).

Question 14

Bond enthalpy down group 7

Answer 14

Strength of covalent bonds decreases down group as atomic radius increases. Bond enthalpy gets less endothermic.

Question 15

First ionisation energy down group 1

Answer 15

decreases down group as atomic radius and shielding increases , outer electron less attracted to nucleus and less energy required to remove therefore, less endothermic.

Question 16

first ionisation energy across period 2

Answer 16

increases across a period. Atomic radius decreases ad shielding remains constant. Outer electron more attracted to the nucleus and more energy required to remove outer electron, more endothermic.

Question 17

First electron affinity down group 7

Answer 17

Atomic radius and shielding increases, outer shell is further from attraction of nucleus. Incoming electron is less attracted to nucleus, becomes less exothermic.

Question 18

first electron affinity across period 2

Answer 18

Atomic radius decreases, shielding remains constant, and outer shell is closer to attraction of nucleus. Incoming electron is more attracted and becomes more exothermic up to group 7.

Question 19

Enthalpy change of solution occurs in 2 steps.

Answer 19

Crystal lattice is separated into ions (endothermic/bonds broken.)
Cations and anions are surrounded by a shell of water and is hydrated (exothermic/ bonds formed.)

Question 20

Enthalpy of hydration

Answer 20

Always exothermic, new bonds are formed.

Question 21

Value of enthalpy of hydration depends on;

Answer 21

charge on ion; larger the charge, the larger enthalpy of hydration.
ionic radius; larger the ionic radius, smaller the enthalpy of hydration.

Question 22

Solubility of gp2 sulfates

Answer 22

Become less soluble. SO42- ion is large and lattice enthalpy approximately constant. Solubility depends on hydration enthalpy of cation which becomes less exothermic down group as cations get larger. Enthalpy of solution becomes less.

Question 23

Why is MgSO4 more soluble than BaSO4?

Answer 23

SO42- ion is large and approximately constant for a ll group 2 sulfates. Solubility depends on hydration enthalpy of cations. Ba2+ is larger so enthalpy of hydration is less exothermic. this means enthalpy of solution will be less exothermic.

Question 24

^Hsol

Answer 24

^Hlatt +^Hhyd (cation) + ^Hhyd(anion)

Question 25

solubility of gp2 hydroxides

Answer 25

Become more soluble. Cations get larger, lattice enthalpy and hydration enthalpy of cation become less exothermic. Lattice enthalpy decreases in magnitude, more than hydration enthalpy. Enthalpy of solution becomes mire exothermic and solubility increases.

Question 26

2nd law of thermodynamics

Answer 26

States spontaneous changes result in an increase in disorder/ entropy.

Question 27

2nd law of thermodynamics determines;

Answer 27

Whether a physical or chemical change will occur at a certain temp.
if redox reactions will occur
equilibrium position