AP Notes Chapter 14

Solutions and Their BehaviorSolutions and Their Behavior

Solutiona homogeneous mixture of two or more components

Solutecomponent(s) present in lesser quantity

Solventcomponent present in greater quantity

A saturated solution contains the maximum quantity of solute that dissolves at that temperature.

An unsaturated solution contains less than the maximum quantity of solute that dissolves at that temperature.

Supersaturated Solutions contain more than is possible and are unstable.

Liquid Solutions1. molarity, M

solution L 1

solute molM

2. mass %

100nsol' mass

AmassA%

3. mole fraction, (A)

nsol' mol

AmolA

solute mol solvent mol

AmolA

1i

4. molality, m

solvent kg

solute molm

MolarSol’n

MolalSol’n

Ideal Solution

P(A)0 is the VP of volatile solvent A at a particular temperature

Properties of Ideal Solutions

if P(A) is the vapor pressure of a solution of

volatile solvent A, and non-volatile solute B,

then P(A) (A)

or P(A) = (A) . P(A)0

[Raoult’s Law]VP Solution

for a solution where 2 components are volatile

P(T) = P(A) + P(B)

= (A) . P(A)0 + (B) . P(B)0

Ideal Solutions

Positive deviation

Real Solutions

Negative deviation

Properties of Ideal Solutions

if P(A) is the vapor pressure of a solution of

volatile solvent A, and non-volatile solute B,

then P(A) (A)

Properties of Ideal Solutions

2. NO volume changes occur

during the solution process

Properties of Ideal Solutions

3. NO heat is evolved or absorbed during

the solution process

Raoult’s Law is valid only for VERY dilute

solutions or some nonpolar - nonpolar

solutions

Solubility Factors

likedissolves

like

Polar H2ONon-polar I2

Non-polar CCl4

Polar H2O

Non-polar I2

Non-polar CCl4

Solvent Extraction

O //H2C-O-C-R | O | //H2C-O-C-R

| O | //H2C-O-C-R a “fat”

+ 3 NaOH

R = (CH2)16CH3

H2C-O-H | | H2C-O-H

| | H2C-O-H

O \\+ 3 R-C-O- Na+

a “soap”

SurfactantsSurfactants

Surface acting agentsSurface acting agents Lowers surface tensionLowers surface tension Enables solvationEnables solvation Those used for cleaning are Those used for cleaning are

commonly called detergentscommonly called detergents

Temperature

SOLIDS

GASES

Pressure

Sg = kHPg

Henry’s Law

ColligativeProperties

Property whose magnitude depends

solely on the concentration of

particles, NOT on the nature of the particles

ElectrolyteElectrolyte

solute that forms solute that forms ions in solution ions in solution

which conducts a which conducts a currentcurrent

Non-ElectrolyteNon-Electrolytesolute that remains solute that remains

as molecules in as molecules in solution which solution which

does NOT conduct does NOT conduct a currenta current

molalitymoles of substance measured through

mass before solution process

takes place

Colligative Properties of

Non-Electrolytes

1. Vapor Pressure LoweringVP Lowering

1. Vapor Pressure Lowering

A = solvent ; B = solute

A + B = 1

1. Vapor Pressure Lowering

A = solvent ; B = solute

A + B = 1

A = 1 - B

but: PA = APo

A

thus: PA = (1 - B) Po

A

or: PA = PoA - BPo

A

oA

AoA

B P

PP

NOTE: the lowering of the vapor pressure of the pure solvent A is a function only of B (solute)

boiling point temperature where vapor pressure of solvent equals the

atmospheric pressure

2. Boiling Point Elevation

Tbp m

Tbp m

Tbp = kbpm

where kbp = a constant that is a function of the solvent

units on kbp ?

units on kbp ?

solute mol

solvent kgK

m

Tkbp

Freezing WaterFreezing Solution

3. Freezing Point Depression

Tfp m

Tfp m

Tfp kfp m

kfp = freezing point constant

kfp = kbp

for the same solvent

OSMOSISthe flow of solvent into

a solution through a semi-permeable

membrane

ExamplesEgg Rxn

Microscopic PerspectiveEgg Explanation

Macroscopic Perspective

4. Osmotic Pressure

the pressure that must be applied to a

solution to stop osmosis

ReverseOsmosis

4. Osmotic Pressure

= osmotic pressure

V = nB R T

or

= MB R T

MB = Molarity of solute

Colligative Properties of Electrolytes

Must adjust for degree of

dissociation

i = van’t Hoff factorTbp = i kbp mTfp = i kfp m

= i

Compound iNaClMgSO4

MgCl2

FeCl3

Compound iNaCl 1.9MgSO4 1.3MgCl2 2.7FeCl3 3.4