Ch. 9: Solutions

Question 1

does the solute or solvent change phase after mixing

Answer 1

the solute changes phase to match the solvent

if already same phases, solvent is present in greater quantity

Question 2

what is solvation

Answer 2

dissolution/hydration

the electrostatic interaction between solute and solvent molecules, how solute becomes homogeneously mixed into solvent

Question 3

when is solvation exothermic

Answer 3

when new interactions between solute and solvent are stronger than the original ones

favored at low temps (new interactions have less energy, and so energy is given off as heat)

Question 4

when is solvation endothermic

Answer 4

when new interactions between solute and solvent are weaker than the original ones

favored at high temps (new interactions have more energy, and so energy is absorbed as heat)

Question 5

what is an ideal solution

Answer 5

stability of new interactions = old interactions

enthalpy of dissolution is zero

Question 6

what does solubility measure

Answer 6

the maximum amount of substance that can be dissolved in a particular solvent at a given temperature

Question 7

when is a solution saturated

Answer 7

when the maximum amount of solvent has been added and any additional solvent will not dissolve

Gibbs free energy is positive, nonspontaneous

Question 8

what does a solute do when it precipitates

Answer 8

remains in solid form

Question 9

how much solute is in a dilute solution

Answer 9

a small amount relevant to the amount of solvent

Question 10

how much solute is in a concentrated solution

Answer 10

a large amount relevant to the amount of solvent

Question 11

what are sparingly soluble salts

Answer 11

solutes that dissolve minimally into the solvent

molar solubility under 0.1 M

Question 12

what is the solvent of an aqueous solution

Answer 12

water

Question 13

how do hydronium ions (H3O+) form

Answer 13

transfer of hydrogen ion from a molecule in solution to a water molecule

typically occurs with acids

Question 14

which group of metal salts are soluble (absolute solubility rules)

Answer 14

all salts of group 1 metals are water soluble

Question 15

which nitrate salts are soluble (absolute solubility rules)

Answer 15

all salts containing nitrate are water soluble

Question 16

what is a complex ion

Answer 16

coordination compound

molecule in which a cation is bonded to at least one electron pair donor (ligand)

Question 17

what are ligands

Answer 17

electron pair donor molecules in a coordination compound

Question 18

what is a chelation

Answer 18

a complex ion in which the central cation is bonded to the same ligand in multiple places

Question 19

what does concentration measure

Answer 19

the amount of solute dissolved in a solvent

Question 20

how is percent composition by mass calculated

Answer 20

mass of solute / mass of solution x 100%

Question 21

how is mole fraction (X) calculated

Answer 21

Xa = moles of A / total moles of all species

Question 22

how is molarity (M) calculated

Answer 22

M = moles of solute / liters of a solution

Question 23

how is molality (m) calculated

Answer 23

m = moles of solute / kg of solvent

Question 24

what does normality (N) of a solution represent

Answer 24

number of equivalents of interest per L of solution

reaction dependent

Question 25

what is the dilution formula

Answer 25

MiVi = MfVf

Question 26

when is a solution in equilibrium

Answer 26

at the saturation point/when it is saturated

rates of dissolution and precipitate are equal

Question 27

what is the solubility product constant (Ksp) equal to

Answer 27

for AmBn, equilibrium constant for its solubility in an aqueous solution

Ksp = [A^n+]^m * [B^m-]^n

ex: for AgCl, Ksp = [Ag+][Cl-]

Question 28

why should Ksp expression never have denominators

Answer 28

because pure solids and liquids are never included the equilibrium constant

Question 29

what is ion product (IP) analogous to

Answer 29

reaction quotient (Q)

a determination of where the system is with respect to its equilibrium position

Question 30

for what IP value is the solution unsaturated

Answer 30

IP < Ksp

Question 31

for what IP value is the solution at equilibrium

Answer 31

IP = Ksp

Question 32

for what IP value is the solution supersaturated

Answer 32

IP > Ksp

Question 33

what is the common ion effect

Answer 33

reduction in molar solubility when a salt is dissolved in a solution that already contains one of its constituent ions

Question 34

what are colligative properties dependent on

Answer 34

physical properties of solutions dependent on concentration of dissolved particles rather than their identity

Question 35

equation for Raoult’s law

Answer 35

Pa = XaPa degrees

vapor pressure of solvent A = mole fraction solvent A * vapor pressure of solvent A in pure state

Question 36

what does Raoult’s law suggest/phenomenon of vapor pressure depression

Answer 36

as solute B is dissolved in solvent A, the vapor pressure of solvent A will decrease and evaporation rate is reduced

Question 37

what is the phenomenon of boiling point elevation

Answer 37

as solute is dissolved into solvent, the boiling point of the new solution is greater than pure solution

Question 38

equation for change in boiling point

Answer 38

delta Tb = iKbm

increase in BP = van’t Hoff factor * proportionality constant * molality

Question 39

what is the phenomenon of freezing point depression

Answer 39

as solute is dissolved in solvent, the freezing point of the new solution is lower than than pure solution

Question 40

equation for change in freezing point

Answer 40

delta Tf = iKfm

increase in FP = van’t Hoff factor * proportionality constant * molality