Chapter 1 Properties of Solutions Introduction 1. Nature of Solutions 2. Solubility 3. Mixing Aqueous Solutions 4. Hydrolysis Table of Contents
Mar 20, 2016
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
• 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 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 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
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