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Question 1

lattice enthalpy definition

Answer 1

measure of the strength of ionic bonding in a giant ionic lattice

Question 2

what is the purpose of Born- Haber cycles

Answer 2

determines the lattice enthalpy indirectly

Question 3

what sort of energy change is needed to form gaseous atoms? why?

Answer 3

• endothermic

- involves breaking bonds

Question 4

what sort of energy change is needed to form gaseous ions?

Answer 4

endothermic

Question 5

what sort of energy change is needed to form a lattice

Answer 5

exothermic

Question 6

standard enthalpy change of formation definition

Answer 6

formation of 1 mol of a compound from its elements in its standard states under standard conditions

Question 7

standard enthalpy change of atomisation definition

Answer 7

formation of one mole of gaseous atoms from the element in its standard states under standard conditions

Question 8

first electron affinity definition

Answer 8

addition of 1 mol of electrons to 1 mol of gaseous atoms to form 1 mol of gaseous 1- ions

Question 9

enthalpy change of hydration definition

Answer 9

dissolving of 1 mol of gaseous ions in water

Question 10

explain why the 2nd ionisation is more endothermic than the 1st ionisation

Answer 10

• Mg+ has one more proton than electrons
• increase nuclear attraction
• decrease radius

Question 11

what energy is needed in the second electron affinity

Answer 11

enothermic

Question 12

what energy is needed in the second electron affinity

Answer 12

endothermic

Question 13

write the equation to calculate energy change

Answer 13

q=mc∆T

Question 14

what 2 processes take place when ionic compounds dissolve in water

Answer 14

• ionic lattice breaks up

- water molecules are attracted to, and surround, the ions

Question 15

what are the general properties of ionic compounds?

Answer 15

• high melting and boiling points
• soluble in polar solvents
• conduct electricity when molten or in aqueous solution

Question 16

effect of ionic size on lattice enthalpy

Answer 16

• ionic radius increases
• attraction between ions decrease
• lattice enthalpy less negative
• melting point decreases

Question 17

effect of ionic charge on lattice enthalpy

Answer 17

• ionic charge increases
• attraction between ions increase
• lattice energy becomes more negative
• melting point increases

Question 18

effect of ionic charge size from left to right

Answer 18

• increasing charge gives more attraction

- decreasing size gives more attraction

Question 19

effect of ionic charge size from right to left

Answer 19

• increasing charge gives more attraction

- increasing size gives less attraction

Question 20

effect of ionic size on hydration enthalpy down group 1

Answer 20

• ionic radius increases
• attraction between ion and water molecules decreases
• hydration energy less negative

Question 21

effect of ionic size on hydration enthalpy down group 1

Answer 21

• ionic radius increases
• attraction between ion and water molecules decreases
• hydration energy less negative

Question 22

effect of ionic charge on hydration enthalpy

Answer 22

• ionic charge increases
• attraction with water molecules increases
• hydration energy become more negative

Question 23

what can entropy be used to predict

Answer 23

• a gas spreading through a room
• heat from a fire spreading through a room
• ice melting in a hot room

Question 24

general rules of entropy

Answer 24

• solids have the smallest entropies
• liquids have greater entropies
• gases have the greatest entropies

Question 25

what will the entropy change be if a system changes to become more random

Answer 25

• energy becomes more spread out

- ∆S is positive

Question 26

what will the entropy change be if a system changes to become less random

Answer 26

• energy becomes more concentrated

- ∆S is negative

Question 27

when any substance changes state from solid to liquid to gas, its entropy increases:

Answer 27

• melting and boiling increase the randomness of particles

- energy is spread out more and ∆S is positive

Question 28

describe the entropy of this reaction:

N₂(g) +3H₂(g) -> 2NH₃(g)

Answer 28

• decrease in the randomness of particles

- energy is spread out less and ∆S is negative

Question 29

standard entropy of a substance

Answer 29

entropy of 1 mole of a substance, under standard conditions (100kPa and 298K)

Question 30

standard enthalpy facts

Answer 30

• JK⁻¹mol⁻¹

- always positive

Question 31

calculate entropy changes

Answer 31

∆S=ΣS(products)-ΣS(reactants)

Question 32

calculate entropy changes

Answer 32

∆S=ΣS(products)-ΣS(reactants)

Question 33

write the Gibb’s equation

Answer 33

∆G=∆H-T∆S

Question 34

enthalpy change, ∆H

Answer 34

heat transfer between the chemical system and the surroundings

Question 35

entropy change at the temperature of the reaction, T∆S

Answer 35

dispersal of energy within the chemical system itself

Question 36

conditions for feasibility

Answer 36

• ∆G<0

Question 37

limitations of predictions made for feasibility

Answer 37

rate of reaction is very slow