Chapter 1 Properties of Solutions

Introduction

1. Nature of Solutions

2. Solubility

3. Mixing Aqueous Solutions

4. Hydrolysis

Table of Contents

• Make a list of mixtures.

• Separate your list into homogeneous and heterogeneous.

• What are the mixtures that we use in life?

Warm Up

Properties of SolutionsChapter 1

Introduction

• There are many kinds of mixtures, solid, liquid or gas

according to physical state as well as electrolyte or non

electrolyte according to electrical conductivity.

• Mixtures can be either homogeneous or heterogeneous

according to structure.

• They are affected from temperature and pressure.

Chapter 1

1. Nature of Solutions

• Mixtures can be either homogeneous or heterogeneous.• The particles of a heterogeneous mixture are large

enough to see under a microscope. Oil in water, sand in water, soup, milk, blood, soil…etc.

• In a homogeneous mixture, however, the particles are molecule-sized, so the mixture appears uniform, even under a microscope. Salty water, cola, copper sulfate solution, steel, coins, fog…etc.

• A solution is a homogeneous mixture of two or more

substances uniformly dispersed throughout a single

phase.

Chapter 1

Chapter 1 1. Nature of Solutions

Chapter 1 1. Nature of Solutions

• Solution = Solvent + Solute(s)

• Solvent is the component of solution in the largest amount

or that determines the state of solution.

• Solute is the part of solution dissolved in a solvent.

• Solutions in which water is the solvent are called aqueous

solutions.Example 1

Find the solute and solvent components of the following solutions.

a. Air b. sea water c. bronze d. Vinegar

Chapter 1 1. Nature of Solutions

An alloy is a homogeneous solution of two or more elements,

at least one of which is a metal. For example, steel, coins,

bronze, brass, solder, amalgam…etc.

Chapter 1 1. Nature of SolutionsThe Dissolution Process• Dissolution is the mixing of a solute in a solvent.

Chapter 1 1. Nature of SolutionsHeat Change in Dissolution Process

• Dissolution process can be either exothermic or

endothermic process with respect to nature of solution. For

example;

• dissolution of NaCH3COO in water is exothermic

process, increases the temperature to 54oC. (Heat Pack)

• but dissolution of NH4NO3 is endothermic, decreases the

temperature to 5oC. (Cold Pack)

Chapter 1 1. Nature of SolutionsConductivity of Solutions

• Solutions that conduct electricity are called electrolytes.

Salt, acid or base solutions are electrolytes.

• Strength of conductivity depends upon the ionization of

solute.

• If it ionizes completely it is called strong electrolyte.

• If the ionization is poor, it is called weak electrolyte.

• Solutions that cannot conduct electricity are called non

electrolyte.

1. Nature of SolutionsConductivity of Solutions

Chapter 1

1. Nature of Solutions

Change in Freezing and Boiling Points

• Solutions boil at higher temperature and freeze at lower

temperatures than pure liquids. Meaning more solute in a

solution decreases the freezing point and increases the

boiling point of solvent.

• Salt is scattered on roads to prevent the freezing, or

antifreeze is added to radiators in cars to prevent both

freezing and boiling of water.

Chapter 1

1. Nature of SolutionsDilute and Concentrated Solutions• Solutions that contain relatively large amount of solute are called concentrated, and relatively small amount of solute are called dilute.

• Dilution is simply adding water to more concentrated solution to make it dilute.

Dilute solutions Concentrated solutions

Chapter 1

2. Solubility• The solubility of a compound is the maximum amount of solute dissolved in a given amount of solvent to form a saturated solution at a particular temperature.

• When a solution contains as much solute as it can dissolve, it is saturated. When it contains less solute than it can dissolve it is called unsaturated.

• If the maximum amount of solute dissolved in 100 g water is less than 0.1 g this solute is accepted as insoluble.

• The solute that has a solubility range 0.1 g to 1 g it is called slightly soluble.

• If the amount of solute is more than 1 g then it is soluble.

Chapter 1

2. SolubilityExample 2

The solubility of NaCl is 38g/100 water at 20oC. How many

gram of saturated solution can be prepared by mixing 95 g

NaCl with enough water at 20oC.

Solution

100 g water is used for 38 g NaCl

X g 95 g

total

100.95 250 g of water must be used38

m of solution = 250 + 95 = 3 5 g 4

x

Chapter 1

2. SolubilityExample 3

The solubility of KNO3 is 30g/100 water at 20oC. How many

gram of water must be used to prepared a saturated solution

containing 120 g KNO3 at 20oC.

Solution

100 g water is used for 30 g KNO3

X g 120 g

400 g of water m100 ust.12030

be usedx

Chapter 1

2. Solubility

1. Temperature

• The solubility of solids usually increase as the temperature

rises. There are some exceptions to this rule; Ce2(SO4)3.

• The solubility of gases decrease as the temperature rises.

Factors Affecting Solubility

2. Pressure

• The solubility of gases in liquids increase as the pressure

above the liquid is increased.

Chapter 1

2. SolubilityFactors Affecting Solubility

Chapter 1

2. SolubilityFactors Affecting Solubility Example 4

When 40 g of NaCl is added in 60 g water, 4 g NaCl remains

undissolved. What is the solubility of NaCl in 100 g water at

the same temperature?

Solution

NaCl= 40-4=36 g in 60 g waterif 36 g NaCl 60 g waterx g 100gwater

100.3 60 g 6 Na60

Cl

dissolvedm

x

Chapter 1

2. SolubilityFactors Affecting Solubility Example 5Solubility of a salt X is 20 g / 100g water at room temperature. 100 g of water is added into 360 g saturated solution of the salt X . How many grams of the salt X must be added to make the new solution saturated?Solution

360 g solution contains 300 g water and 60 g salt X.The new solution has 300 + 100 =400 g water totally.

100 g water dissolves 20 g salt X400 g x g

400.20 80 g X, then100

x 20 g salt X must80 be- 60 = added

Chapter 1

2. SolubilityFactors Affecting Solubility Example 6The solubility of KNO3 at 60 oC is 110 g/100 g water. 220 g of KNO3 is dissolved in 250 g of water at 60 oC. How many grams of water should be evaporated from the solution to make the solution saturated?

Solution

3

3

110 g KNO is dissolved in 100 g water.220 g KNO is dissolved in 200 g water.

Therefore, 250-200=must be evaporated to make the solution s

50 gatur

a

waterted.

Chapter 1

2. SolubilityFactors Affecting Solubility Example 7A saturated solution of the salt X is prepared with 75 g of water at 10 0C . If 30 g of the salt is added and the temperature is increased to 40 0C, how many g salt x precipitates?

Solutionoat 10 C, 100 g water dissolves 20 g salt X

75 g x g 75.20 15g salt x exist.100

x

Chapter 1

2. SolubilityFactors Affecting Solubility

Solutionoat 40 C, 100 g water dissolves 50 g salt X

75 g x g 75.50 37.5g salt x must be.100

x

total mass of salt X is 15+30=45gmass of salt X precipitated is 45 - 37. 75 = .5 g

Chapter 1

3. Mixing Aqueous Solutions

• Precipitation is the formation of a solid in a solution during a

chemical reaction.Pb(NO3)2 (aq) + 2KI(aq) PbI2 (s) + 2KNO3 (aq)

yellow ppt

• An equation that includes only the actual participants in a

reaction is called net ionic equation.

Pb+2 (aq) + 2I-(aq) PbI2 (s)

Chapter 1

3. Mixing Aqueous Solutions

HgCl2 (aq) + 2KI(aq) HgI2 (s) + 2KCl(aq)

Chapter 1

3. Mixing Aqueous Solutions

Pb(NO3)2 (aq) + 2KI(aq) PbI2 (s) + 2KNO3 (aq)

Chapter 1

3. Mixing Aqueous Solutions

AgNO3(aq) + NaOH(aq) AgOH(s) + NaNO3(aq)

Chapter 1

4. Hydrolysis

• Interaction of an ion with water is called hydrolysis.

• The salts of strong acids and strong bases do not hydrolyze,

and form neutral solutions. (Na+, Cl-, K+, NO3-, SO4

-2, Br-,…etc.)

• The salts of weak bases and strong acids hydrolyze, and form

acidic solutions. (NH4Cl, ZnBr2, CuNO3, …etc)

• The salts of strong bases and weak acids hydrolyze, and form

basic solutions. (NaF, KCH3COO, Li3PO4 …etc)

Chapter 1

4. Hydrolysis

Example 8

Predict whether the solutions of following salts are acidic,

basic or neutral.

a. KCl b. Fe(NO3)2 c. Na2CO3 d. LiF

Solution

a. Neutral b. Acidic c. Basic d. Neutral

Chapter 1

END OF THE CHAPTER 1