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)◦ How is a mixture represented on the

macroscopic level?◦ How is a mixture represented on the particle

level?◦ What is the definition of a solution, solute and

solvent?◦ What is the difference between a

heterogeneous and homogeneous solution?

p. 2 of LA book

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.

How are these different (both macroscopically and on the particle level)?

How does this vary based on solute?

p. 3 of LA book

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 saturated solution shown in Figure 13.1?

Figure 13.1 p. 440

p. 3 of LA book

Review: 12.2 Intermolecular ForcesIM

F –

Pure

Sub

stan

ces

Dispersion forces

Dipole forces

Hydrogen bonding

Interactions between:◦ solute/solute

◦ solvent/solvent

p. 4 of LA book

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

p. 4 of LA book

Review: 12.2 Intermolecular Forces

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

IMF

–M

ixtu

res

p. 4 of LA book

13.2 A Molecular View of the Solution Process Review Practice◦ Think about the solvation process And consider this process on a particle level

◦ Think about solubility And consider what can affect solubility

For solubility, consider the interactions between:◦ solute/solute◦ solvent/solvent◦ solvent/solute

Discussed in Chapter 12 – intermolecular forces (12.2)

p. 5 of LA book

Figure 13.2 p. 441

13.2 A Molecular View of the Solution Process

Balanced equation for heat of solution for NaCl

p. 6-7 of LA book

Interactions between:◦ solute/solute

◦ solvent/solvent

◦ solvent/solute

13.3 Concentration Units

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

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

p. 8-9 of LA book

13.3 Concentration Units

Practice:Often regulated materials in substances (like drinking water) are reported in ppm or ppb. If the allowed amount of silver ions in waste water is 0.4 ppm, how many water molecules are present for 1 silver ion?

p. 10-11 of LA book

13.3 Concentration Units

Practice:Concentrated sulfuric acid used in the lab is 96% H2SO4 by mass. What is the ppm/ppb, molarity, molality and mole fraction of the acid solution?

The density of the solution is 1.83 g·mL–1.

p. 11-12 of LA book

13.4 Effect of Temperature on Solubility Consider two types of solutes:◦ Solids (ionic)◦ Gases

(Review 1.3 and 6.6)◦ Model a soluble ionic compound (include all

interactions) – use NaCl(aq)◦ Model a soluble gas solution (include all

interactions) – use CO2(aq)◦ What is the heat of solution for NaCl Thermochemical equation Energy diagram

p. 16-17 of LA book

13.4 Effect of Temperature on Solubility

(Review 4.2) Soluble vs. Insoluble ionic compounds

Solubility plot:◦ Solubility (in mass in grams of the solute in

100 g of water)◦ Temperature

p. 18 of LA book

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

p. 18-19 of LA book

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

p. 20 of LA book

13.4 Effect of Temperature on Solubility – gases

Figure 13.4 p. 444

p. 20 of LA book

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

solids Pressure and solubility of gases◦ How do we symbolically model a gas (use

oxygen) in solution (use water)?◦ What would happen if we increase the

pressure?◦ What is happening on the particle level?

p. 21 of LA book

13.5 Effect of Pressure on the Solubility of Gases

Figure 13.5 p. 445

p. 21 of LA book

13.5 Effect of Pressure on the Solubility of Gases Pressure and solubility of gases◦ How is this modeled?

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?

p. 22 of LA book

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

p. 23 of LA book

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?◦ Qualitatively (on a particle level)◦ Quantitatively

Vapo

r-pr

essu

re lo

wer

ing

(Rao

ult’s

Law

)p. 23 of LA book

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

p. 24 of LA book

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

)p. 25 of LA book

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

p. 25 of LA book

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

p. 26 of LA book

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?◦ Qualitatively (on a particle level)◦ Quantitatively

Boili

ng-P

oint

Ele

vatio

np. 26 of LA book

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.

Boili

ng-P

oint

Ele

vatio

np. 26 of LA book

Table 13.2 p. 450

13.6 Colligative PropertiesBo

iling

-Poi

nt E

leva

tion

Figure 13.7 p. 449

p. 26 of LA book

13.6 Colligative Properties (Review, 12.1-12.4) How do we model

liquids and solids on the particle level? Which has a greater disorder?

Free

zing

-Poi

nt D

epre

ssio

np. 27 of LA book

Figure 13.7 p. 449

What is freezing-point depression?◦ Qualitatively (on a

particle level)◦ Quantitatively

13.6 Colligative Properties

PracticeAt 0oC, 64.447 mass fraction of a saturated aqueous sugar solution is sugar.What is the freezing point of a saturated sugar solution (saturated at 0oC)?

Free

zing

-Poi

nt D

epre

ssio

n

Table 13.2 p. 450

p. 27 of LA book

13.6 Colligative Properties (Review, 13.1) What is vapor pressure? (Review, 12.6) What is osmosis? What is osmosis?

Osm

osis

and

Osm

otic

Pre

ssur

ep. 28 of LA book

Figure 13.9 p. 453

13.6 Colligative PropertiesO

smos

is a

nd O

smot

ic P

ress

ure

Figure 13.8 p. 452

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

p. 28 of LA book

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◦ Qualitatively◦ Quantitatively

Osm

osis

and

Osm

otic

Pre

ssur

ep. 28 of LA book

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

ep. 28 of LA book

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

p. 29 of LA book

13.6 Colligative Properties How are nonelectrolytes and electrolytes

different? (Review 2.6 and 2.7) How do we represent

NaCl or MgCl2 in solution? How is this incorporated into the relationships

for colligative properties?

Elec

trol

yte

Solu

tions

p. 29 of LA book

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

p. 29 of LA book

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

p. 29 of LA book