5.3 Specific types of equilibria

Question 1

features of structure of ionic compound
(1) form
(2) attraction
(3) bonding

Answer 1

(1) crystalline lattice
(2) electrostatic attraction extends throughout lattice
(3) ionic

Question 2

features of the structure of water
*is a molecule
(1) bonding
(2) polarity

Answer 2

(1) covalent
(2) polar, bent (due to large electroneg. difference between H and O)

Question 3

process of dissolution in water
(1+2) attraction
(3) which bonds broken and formed

Answer 3

(1) partially negative oxygen ions in H2O attracts [the cation]
(2) partially positive hydrogen ions in H2O attracts [the anion]
(3) ionic bonds broken; ion-dipole bonds formed

Question 4

a solute dissolves in a solvent when:

Answer 4

solute-solvent attractive forces overcome solute-solute and solvent-solvent attractive forces

Question 5

(2) what solubility depends on

Answer 5

(1) energy required to separate lattice ions
(2) energy released during ion hydration

Question 6

what energy required to separate lattice ions depends on

Answer 6

strength of ionic bonding

Question 7

(3) what strength of ionic bonding depends on

Answer 7

(1) spatial arrangement of ions in lattice
(2) ion size
(3) ion charges

Question 8

(3) what strength of ion-dipole bonding depends on

Answer 8

(1) ion size
(2) ion charge
(3) geometry of ions

Question 9

the more soluble the salt is,

Answer 9

the more energy released compared to energy needed

Question 10

HSC Q: Describe changes in bonding and entropy when KCl dissolves in water.

(1) define KCl and water
(2) detail the dissolution process
(3) which bonds broken, which formed?
(4) entropy and why

Answer 10

(1) KCl is salt with covalent bonding, water is polar molecule with hydrogen bonding
(2) partially neg. O attracts K+; partially pos. H attracts Cl-;
(3) ionic bonds broken, ion-dipole bonds formed
(4) salt lattice is broken, ions disperse, thus entropy increases

Question 11

ΔH, ΔS in separating solvent molecules

Answer 11

endothermic, positive entropy

Question 12

ΔH, ΔS in solute dissolution

Answer 12

endothermic, positive entropy

Question 13

ΔH, ΔS in ion hydration

Answer 13

exothermic, negative entropy

Question 14

list range of solubility

Answer 14

Insoluble < 0.01 mol L-1
Soluble > 0.1 mol L-1
Slightly soluble 0.01 – 0.1 mol L-1

Question 15

solution is SATURATED when…

Answer 15

solution can dissolve as much solute as will be dissolved at that temperature

Question 16

solution is UNSATURATED when…

Answer 16

solution that has not reached the limit of solute it will dissolve

Question 17

solution is SUPERSATURATED when…

Answer 17

solution that contains more dissolved solute than a saturated solution under the same conditions

Question 18

explain dynamic equilibrium in saturated solutions

Answer 18

equilibrium reached between crystallisation and dissolution (ions break away from crystal into solution and ions in solution precipitate out to solid at equal rates)

Question 19

solubility of most solids as temperature increases:

Answer 19

increases

Question 20

solubility of all gases as temperature increases:

Answer 20

decreases

Question 21

what is a precipitate

Answer 21

formed solid in a solution

Question 22

solubility product expression

Answer 22

Ksp = [S] [S]

Ksp = equilibrium constant
higher Ksp = more soluble

Question 23

you can only compare the Ksp of compounds if…

Answer 23

they produce the same number/ratio of ions

Question 24

what is molar solubility

Answer 24

moles of a salt that will dissolve per litre of water to form a saturated solution

Question 25

4 steps to find Ksp from molar solubility

Answer 25

(1) balanced equation and equilibrium expression
(2) construct MICE chart
(3) substitute molar values
(4) find Ksp

Question 26

when ion product < Ksp…

Answer 26

solution is UNSATURATED and NO precipitate forms

Question 27

when ion product >= Ksp…

Answer 27

solution is SATURATED and precipitate forms

Question 28

if Q < Ksp, net reaction…

Answer 28

proceeds to the right (unsaturated)

Question 29

Q = Ksp…

Answer 29

equilibrium, no net change

Question 30

Q > Ksp, net reaction…

Answer 30

proceeds to the left (super saturated)

Question 31

common ion effect

Answer 31

adding a salt to a solution that already contains one of the ions reduces the solubility of the salt

Question 32

toxins present in cycads

Answer 32

cycasin and macrozamin

Question 33

processes used by ATSI to remove toxins in cycads

Answer 33

cooking, pounding/grinding, and then leaching