Physical Properties of Solutions

Physical Properties of Solutions

Types of Solutions (13.1) A Molecular View of the Solution Process

(13.2) Concentration Units (13.3) Effect of Temperature on Solubility (13.4) Effect of Pressure on the Solubility of

Gases (13.5) Colligative Properties (13.6)

General Chemistry I – Concepts Mixtures and representations of matter (1.3 and

1.4) Chemical formulas and nomenclature (2.6 and

2.7) Formula calculations particularly mole

calculations and percent composition (3.3 and 3.5)

Properties of solutions, introduction to hydration and concentrations of solutions (4.1 and 4.5)

Enthalpy and heats of reaction (6.6) Intermolecular forces and vapor pressure (12.2

and 12.6)

13.1 Types of Solutions

(Review 1.3 and 4.1)◦ What is the definition of a mixture and how is

this different from a pure substance?◦ What are the definitions of solute, solvent and

solution?◦ How can you differentiate between a

heterogeneous and homogeneous solution?

13.1 Types of Solutions Key Definitions: Unsaturated solutions:◦ A solution that contains less solute than it has

the capacity to dissolve. Saturated solutions:◦ A solution that contains the maximum amount of

a solute in a given solvent, at a specific temperature.

Using sodium chloride in water describe how these are different.

How would this be different for a solution of silver chloride?

13.1 Types of Solutions

Key Definition: Supersaturated solutions:◦ A solution that contains

more solute than is present in a saturated solution.

What is happening in the supersaturated solution shown in Figure 13.1?

Figure 13.1 p. 440

13.2 A Molecular View of the Solution Process

Consider the intermolecular forces between:◦ solute/solute◦ solvent/solvent◦ solvent/solute

Discussed in Chapter 12 – intermolecular forces (12.2)

Review: 12.2 Intermolecular ForcesIM

F –

Pure

Sub

stan

ces

Dispersion forces

Dipole forces

Hydrogen bonding

Interactions between:◦ solute/solute

◦ solvent/solvent

Review:12.2 Intermolecular Forces

Interactions between solute/solute and solvent/solvent:1. Determine the intermolecular forces of the substances

(usually considering the solubility of two pure substances)

Approximating solubility2. Determine the relative size of the two molecules (same

or different)If both (IMF and size) are the same, then we would approximate that the substances are solubleIf both (IMF and size) are different, then we would approximate that the substances are insolubleIf one (IMF or size) are the same, then we would approximate that the substances are partially soluble

IMF

–M

ixtu

res

Interaction between solvent/solute:◦ Dispersion forces (or induced dipole-induced dipole)

between all substances in a solution.◦ A nonpolar and a polar substance would have induced

dipole-dipole forces◦ A polar and a polar substance would have dipole-dipole

forces◦ A ionic and a nonpolar substance would have ion-induced

dipole forces◦ A ionic and a polar substance would have ion-dipole

forces

Review: 12.2 Intermolecular ForcesIM

F –

Mix

ture

s

Figure 13.2 p. 441

13.2 A Molecular View of the Solution Process

Incorporating energy into the discussion…

13.3 Concentration Units

(Review 3.3, 3.5 and 4.5) What is molarity?

Other types of concentration units:◦ percent by mass◦ molality◦ mole fraction◦ ppm

13.3 Concentration Units

Concentrated sulfuric acid used in the lab is 96% H2SO4 by mass. What is the molarity, molality and mole fraction of the acid solution? The density of the solution is 1.83 g·mL–1.

13.4 Effect of Temperature on Solubility

Consider two types of solutes:◦ Solids (ionic)◦ Gases

(Review, 6.6) What is enthalpy of solution?

13.4 Effect of Temperature on Solubility – ionic solids

SoluteΔHsolnkJ∙mol–1

KNO3 36.5NaNO3 21.56NaBr –0.61KBr 19.87KCl 17.51NaCl 3.87Na2SO4 –5.02

Figure 13.3 p. 444

13.4 Effect of Temperature on Solubility – ionic solids

What does 100 g of potassium nitrate in 100 g water look like at 40oC?

What does this same mixture look like at 70oC?

Figure 13.3 p. 444

13.4 Effect of Temperature on Solubility – gases

Figure 13.4 p. 444

13.5 Effect of Pressure on the Solubility of Gases Pressure and solubility of liquids and

solids Pressure and solubility of gases◦ Using oxygen gas in solution (use water)

describe what is the balanced equation?◦ What would happen if we increase the

pressure?◦ What is the relationship between pressure

and the solubility of gases?

13.5 Effect of Pressure on the Solubility of Gases

Figure 13.5 p. 445

13.5 Effect of Pressure on the Solubility of Gases Pressure and solubility of gases◦ What is the equation for Henry’s law?

Practice:The solubility of carbon dioxide in water at 25oC and 1 atm is 0.034 mol·L–1. What is the mass of carbon dioxide found in a 355 mL can of soda at 25oC, assuming that the manufacturer used a pressure of 2.0 atm of carbon dioxide to carbonate the beverage?

Does Henry’s law always hold? When does it not?

13.6 Colligative Properties

What are colligative properties?◦ Vapor pressure lowering (Raoult’s Law)◦ Boiling-point elevation◦ Freezing-point depression◦ Osmotic pressure

Why could these be useful?

Will first discuss nonelectrolyte solutions

13.6 Colligative Properties

(Review, 12.6) What is vapor pressure? (Review 13.3) What is mole fraction? If something is nonvolatile, what does that

mean?

What is vapor pressure lowering?

Vapo

r-pr

essu

re lo

wer

ing

(Rao

ult’s

Law

)

13.6 Colligative Properties

Practice (nonvolatile solutions)

The solubility of sugar in water at 25oC is 67.47 mass fraction of sugar. What is the vapor pressure of water in this solution?

Vapo

r-pr

essu

re lo

wer

ing

(Rao

ult’s

Law

)

Table 5.2 p. 156

13.6 Colligative Properties

(Review, 12.6) What is vapor pressure? (Review 13.3) What is mole fraction? If something is volatile, what does that

mean?

How does combining two volatile substances to form a solution affect the vapor pressures of each substance?

Vapo

r-pr

essu

re lo

wer

ing

(Rao

ult’s

Law

)

13.6Colligative Properties

Figure 13.6 p. 449

Vapo

r-pr

essu

re lo

wer

ing

(Rao

ult’s

Law

)

Figure 13.6 p. 449

13.6 Colligative Properties Practice (volatile

solutions)

Using figure 13.6, what is the vapor pressure of benzene at 80oC? What is the vapor pressure of toluene at 80oC?

What is the total pressure when 50 g of toluene and 50 g of benzene are mixed?

Vapo

r-pr

essu

re lo

wer

ing

(Rao

ult’s

Law

)

Figure 13.6 p. 449

13.6 Colligative Properties

(Review, 12.7) On a phase diagram where is the normal boiling point located?

What happens at this point?

Boili

ng-P

oint

Ele

vatio

n

Figure 12.32 p. 427

13.6 Colligative Properties (Review, 12.7) On a phase diagram where

is the normal boiling point located? What happens at this point? (Review 13.3) What is molality? Why is molality better than molarity?

What is boiling-point elevation? How is boiling-point elevation quantified?

Boili

ng-P

oint

Ele

vatio

n

13.6 Colligative PropertiesBo

iling

-Poi

nt E

leva

tion

Figure 13.7 p. 449

13.6 Colligative Properties

Practice

What is the boiling point of a saturated sugar solution (saturated at 25oC)?

At 25oC, 67.47 mass fraction of the solution is sugar.Bo

iling

-Poi

nt E

leva

tion

13.6 Colligative PropertiesBo

iling

-Poi

nt E

leva

tion

Table 13.2 p. 450

13.6 Colligative Properties (Review, 12.1-12.4) What is the definition

of a liquid versus a solid? Which has a greater disorder? (Review 13.3) What is molality? Why is molality better than molarity?

What is freezing-point depression? How is freezing-point depression

quantified?

Free

zing

-Poi

nt D

epre

ssio

n

13.6 Colligative PropertiesFr

eezi

ng-P

oint

Dep

ress

ion

Figure 13.7 p. 449

13.6 Colligative Properties

Practice

What is the freezing point of a saturated sugar solution (saturated at 0oC)?

At 0oC, 64.447 mass fraction of the solution is sugar.Fr

eezi

ng-P

oint

Dep

ress

ion

13.6 Colligative PropertiesFr

eezi

ng-P

oint

Dep

ress

ion

Table 13.2 p. 450

13.6 Colligative Properties

(Review, 13.1) What is vapor pressure?

(Review, 12.6) What is osmosis?

Osm

osis

and

Osm

otic

Pre

ssur

e

13.6 Colligative PropertiesO

smos

is a

nd O

smot

ic P

ress

ure

Figure 13.9 p. 453

13.6 Colligative Properties

(Review, 13.1) How do we model solutions on the particle level?

(Review, 12.6) How do we model vapor pressure on the particle level?

What happens if a semi-permeable membrane is placed between a solvent and a solution?

Osm

osis

and

Osm

otic

Pre

ssur

e

13.6 Colligative PropertiesO

smos

is a

nd O

smot

ic P

ress

ure

Figure 13.8 p. 452

13.6 Colligative Properties (Review, 13.1) How do we model

solutions on the particle level? (Review, 12.6) How do we model vapor

pressure on the particle level? What happens if a semi-permeable

membrane is placed between a solvent and a solution?

What is osmosis and osmotic pressure How is osmotic pressure quantified?

Osm

osis

and

Osm

otic

Pre

ssur

e

13.6 Colligative Properties

Practice

The molar mass of a type of hemoglobin was determined by osmotic pressure of 4.60 mmHg for a solution at 20oC containing 3.27 g of hemoglobin in 0.200 L of solution. What is the molar mass of hemoglobin?

Osm

osis

and

Osm

otic

Pre

ssur

e

13.6 Colligative Properties

What are colligative properties?◦ Boiling-point elevation◦ Freezing-point depression◦ Osmotic pressure

What do colligative properties depend on?

Will now discuss electrolyte solutions

Elec

trol

yte

Solu

tions

13.6 Colligative Properties How are nonelectrolytes and electrolytes

different? (Review 2.6 and 2.7) How is a solution of

calcium chloride different from sodium chloride?

How is this incorporated into the relationships for colligative properties?

Elec

trol

yte

Solu

tions

13.6 Colligative Properties

Electrolyte solutions – van’t Hoff Factors

Elec

trol

yte

Solu

tions

Table 13.3 p. 457

13.6 Colligative Properties Why are the

measured values not equal to the calculated values?

What are ion pairs?

Elec

trol

yte

Solu

tions

Figure 13.11 p. 457

13.6 Colligative Properties

Practice:

What is the freezing point of a solution made by dissolving 10 g of sodium chloride in 100 g of water?

What mass of magnesium chloride would be needed for the same change in freezing point?

Elec

trol

yte

Solu

tions