Ch 12.1 Types of Mixtures

Chapter 12.1

Standard 6.a.: Students know the definitions of solute and solvent.

Objectives: We will distinguish between heterogeneous

and homogeneous mixtures We will compare the properties of

suspensions, colloids, and solutions.

Heterogeneous vs. Homogeneous Mixtures

Heterogeneous Mixture: mixture does not have a uniform composition. Ex: Milk and soil

Homogeneous Mixture: entire mixture has the same or uniform composition. Ex: Salt water

Solutions

Soluble: capable of being dissolved. Ex. Sugar is soluble in water.

Sugar and water create a solution, or a homogeneous mixture of two or more substances in a single phase.

Solvent: the thing that does the dissolving. Solute: the thing that is being dissolved.

Solutions may exist as gases, liquids, or solids, and may also be combinations.

Solute State Solvent State Example

Gas Gas Oxygen in Nitrogen

Gas Liquid CO2 in Water

Liquid Liquid Alcohol in Water

Liquid Solid Mercury in Silver & Tin

Solid Liquid Sugar in Water

Solid Solid Copper in Nickel (alloy)

Suspensions

Suspension: When the particles in a solvent are so large that they settle out unless the mixture is constantly agitated. Ex: Muddy water

The particles in a suspension can be separated by passing the mixture through a filter.

Colloids Particles that are intermediate in size between

those in solutions and suspensions form mixtures called colloids.

These are also known as emulsions and foams and cannot be separated using a filter. Ex. Mayonnaise and Milk

Tyndall Effect: when light is scattered by the particles in a colloid.

*Table 3 on page 404 lists the properties of solutions, colloids, and suspensions.

Solutes: Electrolytes vs. Nonelectrolytes

Electrolyte: a substance that dissolves in water to give a solution that conducts an electric current.

Nonelectrolyte: a substance the dissolves in water to give a solution that doesn’t conduct an electric current.

Chapter 12.1

Standard 6.a.: Students know the definitions of solute and solvent.

Objectives: We will distinguish between heterogeneous

and homogeneous mixtures We will compare the properties of

suspensions, colloids, and solutions.

Homework

Ch 12.1 pg 406 #1-4, 6

Ch 12.2 The Solution Process

Chapter 12.2

Standard 6.c.: Students know temperature, pressure, and surface area affect the dissolving process.

Objectives: We will list the 3 factors that affect that

rate of dissolution. We will compare the effects of temperature

and pressure on solubility.

Factors Affecting Dissolution Rate

The compositions of the solvent and the solute determine whether a substance will dissolve.

Three factors that affect dissolving rate: Stirring (agitation) Temperature Surface area of the dissolving particles.

Solubility Solution Equilibrium: the physical state in

which the opposing processes of dissolution and crystallization of a solute occur at equal rates.

Solubility tells us how much solute can dissolve in a certain amount of solvent at a particular temperature and pressure to make a saturated solution. Expressed in grams of solute per 100 grams of

solvent

Saturated Solution: the solution cannot hold any more solute.

Unsaturated Solution: the solution could still dissolve more solute.

Supersaturated Solution: the solution is holding more than it should at the given temperature, and if you messed with the solution by shaking it or adding even one more crystal of solute, the whole thing would crystallize rapidly.

Solubility Values: amount of substance required to form a saturated solution with a specific amount of solvent at a specified temperature.

Solubility of sugar is 204 grams per 100 grams of water at 20°C.

Solute-Solvent Interactions

“Like dissolves Like” Polar will dissolve other polar molecules

and Nonpolar dissolves other nonpolar. Hydration: when water is used to dissolve

an ionic solution.

Liquid Solutes and Solvents Miscible: two liquids that can dissolve in

each other. Immiscible: the liquids don’t mix.

Ex. Oil and vinegar

Factors Affecting Solubility

Temperature affects the solubility of: Solid Solutes Liquid Solutes Gaseous Solutes

Pressure affects the solubility of: Gaseous Solutes

Temperature Gas dissolved in a Liquid: as the temperature

increases, the solubility decreases. Example: Warm soda loses its carbonation.

Solid dissolved in a Liquid: as the temperature increases, the solubility increases. Example: Sugar in hot tea versus iced tea.

Pressure Gas dissolved in Liquid: As pressure

increases, solubility increases. Example: Soda is carbonated under high pressure.

Solid dissolved in Liquid: As pressure increases, solubility does not change! Since you cannot compress solids and liquids,

pressure has no effect on solubility.

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 above the liquid. So, as the pressure of the gas above the liquid

increases, the solubility of the gas increases.

S1 S2

P1 P2

Calculating Solubility of a Gas If the solubility of a gas in water is 0.77 g/L at 3.5

atm of pressure, what is its solubility (g/L) at 1.0 atm of pressure and a constant temperature? P1 = 3.5 atm

S1 = 0.77 g/L

P2 = 1.0 atm

S2 = ? g/L

0.77 g/L = S2 3.5 atm 1.0 atm

S2 = 0.22 g/L

Enthalpies of Solution Solvated: when a solute particle is

surrounded by solvent molecules. The formation of a solution is accompanied

by an energy change, it can be released or absorbed.

Enthalpy of solution: the net amount of energy absorbed as heat by the solution when a specific amount of solute dissolves in a solvent.

Chapter 12.2

Standard 6.c.: Students know temperature, pressure, and surface area affect the dissolving process.

Objectives: We will list the 3 factors that affect that

rate of dissolution. We will compare the effects of temperature

and pressure on solubility.

Homework

Ch 12.2 pg 426 #7-12

Ch 12.3 Concentrations of

Solutions

Chapter 12.3

Standard 6.d.: Students know how to calculate the concentration of a solute in terms of grams per liter, molarity, ppm, and percent composition.

Objective: We will calculate the concentration of a solute, the amount of solute in a given amount of solution, and the amount of solution that contains a given amount of solute.

Concentrations of Solutions

Concentration of a solution: a measure of the amount of solute that is dissolved in a given quantity of solvent.

Solutions can be referred to as dilute or concentrated, but these are not very definite terms.

Molarity Molarity (M): the number of moles of solute

dissolved in one liter of solution.

Note: it is the total volume in liters of solution, not the liters of solvent.

solution of liters

solute of moles(M)Molarity

Calculating Molarity of a Solution IV Saline Solutions are 0.90 g NaCl in exactly

100 mL of solution. What is the molarity of the solution?

Step 1: convert mL to L (divide by 1000) Step 2: convert the grams of NaCl to moles

of NaCl using molar mass. Step 3: put moles of NaCl and L of solution

into the molarity equation and divide.

Finding Moles of Solute Household bleach is a solution of sodium

hypochlorite (NaClO). How many moles of solute are present in 1.5L of 0.70M NaClO?

Moles Solute = M x L = mol/L x L Multiply the given volume in L by the molarity

expressed in mol/L.

MolalityMolality

Another way to express solution concentration Another way to express solution concentration is is Molality (Molality (mm)) NOT THE SAME AS MOLARITY!NOT THE SAME AS MOLARITY!

MolalityMolality ( (mm) is the concentration of a solution ) is the concentration of a solution expressed in moles of soluteexpressed in moles of solute

solvent kg 1

solute of moles )(molality m

• Calculate the molality of a solution Calculate the molality of a solution prepared by dissolving 10.0g of NaCl prepared by dissolving 10.0g of NaCl in 600.g of water.in 600.g of water.

Calculating Molality of a Solution

m m == mol of solutemol of solute

kg of solventkg of solvent

10.0g NaCl 10.0g NaCl 0.171 mol NaCl 0.171 mol NaCl

== 0.171 mol of NaCl0.171 mol of NaCl

0.600 kg of water0.600 kg of water

600.0 g 600.0 g 0.600 kg 0.600 kg

== 0.285 0.285 mm NaCl NaCl

Finding Moles of Solute using molality.

How many moles of sodium fluoride are How many moles of sodium fluoride are needed to prepare a 0.40needed to prepare a 0.40mm NaF solution that NaF solution that contains 750.0g of water?contains 750.0g of water?

mol NaF= 0.40 mol NaF= 0.40 molmol x 0.75 kg = 0.30 mol x 0.75 kg = 0.30 mol kgkg

mol solute = mol solute = m m x kg of solventx kg of solvent

m m == mol of solutemol of solute

kg of solventkg of solvent

Making Dilutions Diluting a solution reduces the number of

moles of solute per unit volume, but the total number of moles of solute in solution does not change.

M1 x V1 = M2 x V2

Basically, you take a given amount of moles and increase the solvent which decreases the concentration but the amount of moles in the total solution is the same.

Preparing a Dilute Solution How many mL of 2.00M MgSO4 solution must

be diluted with water to prepare 100.0mL of 0.400M MgSO4?

Use the dilution formula and plug in the known values and then solve for the unknown.

Volume can be in any unit, as long as they are both the same. (Just like gas laws).

0.400 M MgSO4 x 100.0 mL = 2.00 M MgSO4 x V2

V2 = 20.0 mL

Chapter 12.3

Standard 6.d.: Students know how to calculate the concentration of a solute in terms of grams per liter, molarity, ppm, and percent composition.

Objective: We will calculate the concentration of a solute, the amount of solute in a given amount of solution, and the amount of solution that contains a given amount of solute.

Homework

Ch 12.3 pg 427 #21-23 and 27-29