Oceans - Enthalpies of Solution

Question 1

how are ionic solids held together?

Answer 1

electrostatic attraction between anions and cations

Question 2

what happens to the arrangement of an ionic compound when dissolved in water?

Answer 2

the cations and anions are seperated by water molecules, so the cations and anions now act independently of each other

Question 3

how do cations interact with water when dissolved?

Answer 3

the cations attract the 𝛿 negative oxygens in water, forming a solvation shell

Question 4

how to anions interact with water when dissolved?

Answer 4

attracting the 𝛿 positive hydrogens in water, forming a solvation shell

Question 5

what is a solvation shell?

Answer 5

a molecule that is surrounded by water molecules

Question 6

why won’t all ionic compounds dissolve in water?

Answer 6

not enough energy in the water to seperate the anions and cations

Question 7

what is the process of dissolving an ionic compound?

Answer 7

seperation from lattice

hydration of ions

Question 8

what is the seperation from lattice?

Answer 8

the process of isolating ions from an ionic lattice during dissolving of ionic compounds

Question 9

what is lattice enthalpy?

Answer 9

the enthalpy change when one mole of solid is formed by seperated ions come together

Question 10

is lattice enthalpy endothermic or exothermic?

Answer 10

endothermic

Question 11

what state are ions in after the lattice seperation but before hydration?

Answer 11

gaseous

Question 12

what is the symbol for lattice enthalpy?

Answer 12

ΔH_lattice

Question 13

what happens to an ion when it is hydrated?

Answer 13

when they are bound to water molecules in ion-diplole interactions

Question 14

what effect does charge density have on hydration?

Answer 14

the higher the charge density of an ion, the more hydrated it will be

Question 15

what happens when bonds form between ions and water molecules?

Answer 15

energy is released

Question 16

what can the energy released from hydration be used for?

Answer 16

seperating other ions from the lattice

Question 17

what other factor requires energy that affects the solubility of ionic compounds?

Answer 17

the hydrogen bonds between water molecules need to be broken in order for the ionic compound to dissolve

Question 18

what is the enthalpy of hydration?

Answer 18

the enthalpy change for the formation of a solution of ions from one mole of gaseous ions

Question 19

how can the strength of attraction between ions and water molecules be measured?

Answer 19

the enthalpy of hydration

Question 20

what is the symbol for the enthalpy of hydration?

Answer 20

ΔH_hyd

Question 21

is the enthalpy of hydration exothermic or endothermic?

Answer 21

exothermic

Question 22

what is the enthalpy of solvation and when is it used?

Answer 22

the same as enthalpy of hydration but not specific to water

used when water is not the solvent

Question 23

what is the symbol for the enthalpy of solvation?

Answer 23

ΔH_solv

Question 24

what is the enthalpy change of solution?

Answer 24

the difference between enthalpy of hydration and the lattice enthalpy

Question 25

what is the equation for the enthalpy change of solution?

Answer 25

ΔH_sol = ΔH_hyd(anion) + ΔH_hyd(cation) - ΔH_lattice

Question 26

draw a diagram for a negative enthalpy of solution of an ionic compound

Answer 26

Question 27

draw a diagram for a positive enthalpy of solution for an ionic compound

Answer 27

Question 28

what will happen to ionic compounds with a negative enthalpy of solution?

Answer 28

they will dissolve because the process is energetically favourable

Question 29

what will happen to ionic compounds with a positive enthalpy of solution?

Answer 29

they will not dissolve as the process is energetically unfavourable

Question 30

what are the exceptions to the rule of compounds with positive solution enthalpies not dissolving?

Answer 30

situations where the entropy increase is favourable

Question 31

why won’t ionic solids dissolve in non-polar solvents?

Answer 31

the solvation enthalpy is too small