Types of Mixtures

• Solutions

• Suspensions

• Colloids

Solutions are:

• A homogeneous mixture of two or more substances in a single phase

• Composed of:1. Solvent- the

substance that does the dissolving

2. Solute- the substance that is being dissolved

Example: In sugar water, water is the solvent and sugar is the solute.

Suspensions

• A mixture in which the particles are so large that they settle out unless the mixture is constantly stirred or agitated.

• Ex. a jar of muddy water

Colloids

• A mixture in which the particles are intermediate in size between those in solutions and suspensions.

Ex. paints, milk, mayonaise, fog, chesse

Tyndall Effect

• Colloids appear to be homogeneous mixtures (aka solutions) because the individual particles can not be seen…however, they are not true solutions.

• The particles are large enough to scatter light.

• This effect is known as the Tyndall effect.

Types of Solutions:

• Type of solution is determined by the solvent.

• Gaseous-mixture of two or more gases

• Liquid- solvent is a liquid

• Solid- solvent is a solid

Examples of:1. Gaseous- air,

scuba tanks2. Liquid- tea, Kool-

aid, cokes, salt water

3. Solid- metal alloys, amalgams (dental fillings)

Some solutions conduct electricity:

• Electrolytes- a solution that conducts electricity as a result of the formation of ions in solution (examples: salt water, vinegar)

• Nonelectrolyte- a solution that does not conduct electricity because there is no formation of ions in solution (example: sugar in oil)

Electrolyte

Nonelectrolyte

Factors that Affect Rates of Dissolving Solids in Liquids:

1. Surface Area- increasing surface area increases the rate of dissolving

2. Agitation- stirring or shaking increases rate of dissolving

3. Heat- heating the solvent will increase the rate of dissolving

Solubility

• The amount of a substance that is dissolved at solution equilibrium in a specific amount of solvent at a specified temperature.

• Factors Affecting Solubility:1. Nature of Solute and Solvent-

“like dissolves like”- polar dissolves polar-nonpolar dissolves nonpolar

2. Pressure- changes in pressure have little affect on dissolving solids in liquids but an increase in pressure will increase the solubility of gases in liquids

3. Temperaturea) Increasing temp., decreases gas

solubilityb) Increasing temp., increases solid

solubility

3 Classifications of Solutions

• Saturated- a solution that contains the max. amount of dissolved solute at a given temp.

• Unsaturated- a solution that contains less solute than a saturated solution at a given temp.

• Supersaturated- a solution that contains more dissolved solute than a saturated solution at a given temp.

Solubility Curves:

• Show how much solute can go into solution with a given amount of solvent at different temperatures.

Solubility Curve:

Colligative Properties

• A property that depends on the number of solute particles but is independent of their nature

• 3 Colligative Properties

1. Vapor Pressure Lowering

2. Freezing Point Depression

3. Boiling Point Elevation

• Vapor Pressure Lowering- the vapor pressure of a solvent containing a nonvolatile solute is lower than the vapor pressure of the pure solvent at any temp.

• Freezing Point Depression- the freezing point of a solvent containing a solute will be lower than the pure solvent

• Boiling Point Elevation- the boiling point of a solvent containing a solute will be higher than the pure solvent

Solution Concentration:

• Concentration is a measurement of the amount of solute in a given amount of solvent or solution

• Can be expressed qualitatively or quantitatively

• Qualitative Terms:1. Dilute- relatively small

amount of solute compared to solvent

2. Concentrated- relatively large amount of solute in a solvent

Quantitative Terms:

• Percent by Mass

• Molarity

• Molality

Percent by Mass

• The number of grams of solute dissolved in 100 g of water

Percent by mass = mass solute x100

mass solute + mass solvent

Examples:

• A solution of sodium chloride is prepared by dissolving 5 g of salt in 550 g of water. What is the concentration as given by percent by mass?

Answ: 0.9%• What is the percent by mass of a solution

prepared by dissolving 4 g of acetic acid in 35 g of water.

Answ: 10%

Molarity

• Symbolized by M

• Units of mol

L

• Describes how many moles of solute are present per liter of solution

Examples:• What is the molarity of 3.5 L of solution

that contains 90 g of sodium chloride?Answ: 0.44 M• How many moles of HCl are present in 0.8 L of a 0.5 M HCl solution?Answ: 0.4 mol• How many grams of sodium chloride will

be required to make 555 mL of a 1.45 M solution?

Answ: 47.1 g

More Examples:

• How many liters of solution can be prepared if 78.9 g of sodium chloride is used to make a 3.00 M solution?

Answ: 0.45 L• What is the molarity of a solution that is

prepared by using 20 g of sodium hydroxide in enough water to make a 2 L solution?

Answ: 0.25 M

Dilution Problems

• Use the equation:

M1V1 = M2V2

Where M1 = molarity 1, V1= volume 1….all volumes must be in liters.

Examples:

• What is the molarity of a solution that is made by diluting 50 mL of a 4.74 M solution to 250 mL?

Answ: 0.948 M

Molality

Symbolized by m

Units are mol solute

kg of solvent

Describes how many moles of solute are present per kg of solvent.

Examples:

• A solution contains 17.1 g of sucrose (C12H22O11) dissolved in 125 g of water. Find the molal concentration.

Answ: 0.400 m• How much iodine must be added to

prepare a 0.480 m solution of iodine in carbon tetrachloride (CCl4) if 100 g of CCl4 is used?

• Answ: 12.2 g

More Examples:

• What is the molality of a solution composed of 2.55 g of acetone (CH3)2CO, dissolved in 200 g of water?

Answ: 0.219 m

• What quantity, in grams, of methanol (CH3OH) is required to prepare a 0.244 M solution in 400 g of water?

Answ: 3.12 g

• How many grams of AgNO3 are needed to prepare a 0.125 m solution in 250 mL of water? (Hint.. 1 mL of water = 1g and

1 L of water = 1 kg)

Answ: 5.31 g

Honors:

• What is the molality of a solution that contains 200 g of carbon tetrachloride in 800 mL of chloroform? The density of chloroform is 1.489 g/mL.

Examples:

• 2H3PO4 + 3Ca(OH)2 Ca3(PO4)2 +6 H2O

1. If 2 L of 4 M phosphoric acid is used, how many grams of water could be formed?

2. If 6 g of calcium hydroxide is used, how many liters of a 5 M acid solution would be needed?

More Examples:

3. When 200 mL of 6 M phosphoric acid is used, how many mL of a 3 M calcium hydroxide solution would be required?

4. What is the molarity of 0.6 L of calcium phosphate produced when 500 mL of 3 M phosphoric acid is used?

More Examples:

• Na2CO3 + HCl NaCl + H2O + CO2

5. If the above reaction was performed at STP and 2 L of carbon dioxide gas was collected, what was the molarity of the 200 mL of HCl used?