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What are some special properties of solutions? Chemistry Unit 11

Chem 1 unit 11 presentation

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Chem 1: properties of solutions

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Page 1: Chem 1 unit 11 presentation

What are some special properties

of solutions?Chemistry Unit 11

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Main IdeasMixtures can be either heterogeneous or homogeneous

Concentration can be expressed in terms of percent or in terms of moles

Factors such as temperature, pressure, and polarity affect the formation of solutions

Colligative properties depend on the number of solute particles in a solution

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Types of Mixtures 11.1

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Objectives

Compare the properties of suspensions, colloids, and solutions

Identify types of colloids and types of solutions.

Describe the electrostatic forces in colloids

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Types of MixturesThere are heterogeneous and

homogeneous mixtures:

• Heterogeneous Mixtures are a combination of two or more pure substances in which each pure substance retains its individual properties. There are two main types of heterogeneous mixtures:

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Types of Mixtures

1.Suspensions – A suspension is a mixture containing particles that settle out if left undisturbed but, when stirred, the substance will flow like a liquid. • These substances are called

thixotropic. These particles can be filtered out.

Example : muddy water

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Types of Solutions2. Colloids – A colloid is made of

smaller sizes of suspension particles and these particles do not settle out. Particles cannot be filtered out. The most abundant substance in a mixture is the dispersion medium.

Example: Milk• Colloids are categorized

according to the phases of their particles.

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Types of Colloids

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ColloidsThe dispersed particles in a colloid are prevented from settling out because they often have polar or charged atomic groups on their surfaces. This results in the formation of electrostatic layers around the particles.

The layers electrostatically repel each other when the dispersed particles collide, thus, the particles remain in the colloid.

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Colloids

If you interfere with the electrostatic layering, colloid particles will settle out of the mixture. Heating also destroys a colloid because it gives colliding particles enough kinetic energy to overcome the electrostatic forces and settle out.

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Brownian MotionBrownian motion is the jerky, random movements of particles in a liquid colloid, from the results of particle collisions.

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Tyndall EffectConcentrated colloids are often

cloudy or opaque. Dilute colloids sometimes appear as clear as solutions. Dilute colloids appear to be homogeneous solutions because their dispersed particles are so small.

The Tyndall effect is when dispersed colloid particles scatter light.

Examples: sunlight through smoke filled air or fog

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Homogeneous Mixtures

A homogeneous mixture is a solution of two or more substances that blend easily and constant composition throughout. There are different types of homogeneous solutions:

A solution might exist as a gas, a liquid, or a solid, depending on the state of its solvent. Water is the most common liquid solvent.

Examples: salt water and steel

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Types of Solutions

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Forming Solutions

Some combinations of substances readily form solutions, and others do not.

A substance that dissolves in a solvent is said to be soluble in that solvent.

Example: Sugar in water

Two liquids that are soluble in each other are called miscible.

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Forming SolutionsA substance that does not dissolve in a solvent is said to be insoluble.

Two liquids that cannot be mixed together but separate shortly after are said to be immiscible

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QuestionsMiscible substances are:

A. two liquids that are not soluble in

each other

B. solids that dissolve in liquids

C.solids that do not dissolve in liquids

D. two liquids that are soluble in each other

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Questions

The jerky, random movement of particles in a liquid colloid is known as ____.

A. Brownian motion

B. Tyndall effect

C. Charles’s Law

D. kinetic energy

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Homework

CALM 11.1

p 479 #2, 4, 6,7

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Solution Concentration

11.2

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Objectives

Describe concentration using different units

Determine the concentrations of solutions

Calculate the molarity of a solution.

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Expressing Concentration

Concentration can be expressed in terms of percent or in terms of moles.

The concentration of a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution.

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Expressing Concentration

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Practice Problem #1In order to maintain a sodium chloride

(NaCl) concentration similar to ocean water, an aquarium must contain 3.6g NaCl per 100g of water. What is the percent by mass of NaCl in the solution?

Answer: 3.5%

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Practice Problem #2

120 ml of Sulfuric acid is mixed with 340 ml of water. What is the percent by volume of acid in the solution?

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Molality

Molality is the ratio of moles of solute dissolved in 1 kg of solvent.

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Practice Problem #3

In the lab, a student adds 4.5g of sodium chloride (NaCl) to 100.0g of water. Calculate the molality of the solution.

0.77 mol/kg

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Mole Fraction

Mole fraction is the ratio of the number of moles of solute in solution to the total number of moles of solute and solvent.

where XA and XB represent mole fractions of each substance

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Practice Problem #4

100 g of a hydrochloric acid solution contains 36 g of HCl and 64 g of H2O. What are the mole fractions of HCl and water?

.22 HCl

.78 H2O

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Molarity

Molarity is the number of moles of solute dissolved per liter of solution.

Dilution equation: M1V1 = M2V2

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Practice Problem #5

A 100.5 ml intravenous (IV) solution contains 5.10 g of glucose (C6H12O6). What is the molarity of this solution?

Ans: 0.282M

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Practice Problem #6

If you needed to make a 1.0 M solution of CaCl2, how many grams would you need to make 500 ml of it?

5.5g

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Practice Problem#7:

DilutionWhat volume of 2.00 M calcium

chloride stock solution would you use to make 0.50 L of 0.300 M calcium chloride solution?

75 ml or .075L

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QuestionWhich is NOT a quantitative

measure of concentration?

A. molarity

B. molality

C. percent by mass

D. dilute

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QuestionThe number of moles of solute

divided by liters of solvution is called ____.

A. molarity

B. molality

C. percent by volume

D. percent by mass

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Homework

CALM 11.2

p481-483 #9,10, 16-18

p485-487 # 20-22, 24, 25, 27, 29

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Factors Affecting Solvation

11.3

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Objectives

Describe how intermolecular forces affect solvation.

Define solubility.

Understand what factors affect solubility.

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Solvation

The process of surrounding solute particles with solvent particles to form a solution is called solvation.

Solvation in water is called hydration.

“like dissolves like”

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Solvation

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Factors that Affect Solvation

Agitation – shaken or stirred – agitation of the mixture allows for more contact between solute and solvent.

Surface area – breaking the solute into small pieces helps solvation. A greater surface area allows more collisions to occur.

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Factors that Affect SolvationTemperature – As temperature increases, the rate of solvation also increases. Additionally, hotter solvents generally can dissolve more solid solute.

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Solubility

Solubility is the ability of a solvent to dissolve a solute.

In an aqueous solution, a precipitate forms when a mixture produces an insoluble product.

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Solubility Guidelines

1.All common salts of the group 1 elements and ammonium ions are soluble.

2.All common acetates and nitrates are soluble.

3.All binary compounds of group 17 elements (other than F) with metals are soluble except hoes of silver, mercury (I), and lead.

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Solubility Guidelines

4. All sulfates are soluble except those of barium, strontium, lead, calcium, silver, and mercury (I).

5. Except for those in Rule 1, carbonates, hydroxides, oxides, sulfides, and phosphates are insoluble.

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Practice Problem #8

Which of the following substances would be a precipitate in an aqueous solution? Why?

a) NaCl

b) CaCO3

c) Fe(NO3)

d) KOH

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Solubility

Unsaturated solutions – An unsaturated solution is one that contains less dissolved solute than the solvent can handle at a certain temperature and pressure.

In other words, more solute can be dissolved in an unsaturated solution.

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SolubilitySaturated solution – The

maximum amount of solute has been dissolved in the solvent. The amount of crystallization is at equilibrium with the amount of solvation.

In other words: The solution cannot dissolve anymore solute.

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SolubiltyA supersaturated solution contains

more dissolved solute than a saturated solution at the same temperature and are considered unstable.

To make a supersaturated solution, a saturated solution is formed at a high temperature and then cooled slowly.

The slow cooling allows the excess solute to remain dissolved in solution at the lower temperature.

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Solubility of Gases

Gases, in general, are less soluble at higher temperatures than at lower temperatures. At higher temperatures, the gases have a higher kinetic energy that allows them to escape from a solution.

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Henry’s Law

Pressure affects the solubility of gaseous solutes in solutions. The solubility of a gas in any solvent increases as its external pressure increases.

Carbonated beverages rely on the container to provide enough pressure to keep gas dissolved in the solution.

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Henry’s Law

Henry’s law states that at a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P) of the gas.

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Practice Problem #9If 0.85 g of a gas at 4.0 atm of

pressure dissolves in 1.0 L of water at 25°C, how much will dissolve in 1.0 L of water at 1.0 atm of pressure and the same temperature?

.21 g/ liter

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QuestionFor a given amount, which type

of solution contains the LEAST amount of solute?

A. solvated

B. saturated

C. supersaturated

D. unsaturated

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Question

At a given temperature, the solubility of a gas is directly proportional to what?

A. volume

B. mass

C. molarity

D. pressure

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Homework

CALM 11.3

p497 #36, 37, 39, 41

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Solution Stoichiometry

11.4

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Objectives

Solve solution stoichiometry problems and solution limiting reactant problems.

Determine excess concentration of ions after a reaction.

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Solution Stoichiometry

Stoichiometry applies to solutions too. The number of moles of a reactant and/or product can be found with concentration using the concentration equations.

Most solution stoichiometry utilizes the net ionic equation.

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Solution Stoichiometry

Concentration of ions can be found in a solution by using the ratios in a compound.

For example: 1.0 M CaCl2 has 1.0 mole of Calcium (Ca2+) in 1 liter of solution and 2.0 moles of chloride (Cl-)

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Practice Problem #10

What is the concentration of sodium ions in 1 liter of a 2.0 M solution of sodium sulfate?

4.0 M

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Practice Problem #11

What mass of solid aluminum hydroxide can be produced when 50.0ml of 0.200 M Al(NO3)3 is added to 200.0 ml of 0.100 M KOH?

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Practice Problem #12

A 100.0 ml of 0.200 M aqueous potassium hydroxide is mixed with 100.0 ml of 0.200 M aqueous magnesium nitrate. Write a balanced equation and net ionic equation. What mass of precipitate is produced and what is the concentration of each ion remaining in solution after the reaction is complete.

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Practice Problem #13

What mass of silver chloride can be prepared by the reaction of 100.0ml of 0.20 M silver nitrate with 100.0 ml of 0.15 M calcium chloride? Write the balanced equation and net ionic equation. Calculate the concentration of each ion remaining in solution after precipitation is complete.

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Accumulating Content

11.5

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Accumulating Content

How does the net ionic change the way stoichiometry is calculated? What are the pros and cons?

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Accumulating Content

How does concentration affect solutions?

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Accumulating Content

How is solvation similar to ionic compounds?

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Key Concepts

The individual substances in a heterogeneous mixture remain distinct.

Two types of heterogeneous mixtures are suspensions and colloids.

Brownian motion is the erratic movement of colloid particles.

Colloids exhibit the Tyndall effect.

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Key Concepts

A solution can exist as a gas, a liquid, or a solid, depending on the solvent.

Solutes in a solution can be gases, liquids, or solids.

Concentrations can be measured qualitatively and quantitatively.

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Key Concepts

Molarity is the number of moles of solute dissolved per liter of solution.

Molality is the ratio of the number of moles of solute dissolved in 1 kg of solvent.

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Key Concepts

The number of moles of solute does not change during a dilution.

M1V1 = M2V2

The process of solvation involves solute particles surrounded by solvent particles.

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Key Concepts

Solutions can be unsaturated, saturated, or supersaturated.

Henry’s law states that at a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P) of the gas above the liquid.

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