Solutions

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.

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 tanks 2.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 solutions (ex: sugar in water)

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 3.Temperature

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:

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

Dilution Problems Use the equation: M 1 V 1 = M 2 V 2 Where M 1 = molarity 1, V 1 = volume 1….all volumes must be in liters. EX: What is the molarity of a solution that is made by diluting 50 mL of a 4.74 M solution to 250 mL? Answ: M

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

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 (C 12 H 22 O 11 ) dissolved in 125 g of water. Find the molal concentration. Answ: m How much iodine must be added to prepare a m solution of iodine in carbon tetrachloride (CCl 4 ) if 100 g of CCl 4 is used? Answ: 12.2 g

How many grams of AgNO 3 are needed to prepare a m solution in 250 mL of water? (Hint.. 1 mL of water = 1g and 1 L of water = 1 kg) Answ: 5.31 g

Solution Stoichiometry We will use the same basic principles from molarity (M), except now we are dealing with a reaction, so mole ratios will be used to convert. Stoichiometry WS: 1.2H 3 PO 4 + 3Ca(OH) 2  Ca 3 (PO 4 ) 2 + 6H 2 O 6. Na 2 CO 3 + 2HCl  2NaCl + H 2 O + CO HNO 3 + Al(OH) 3  Al(NO 3 ) 3 + 3H 2 O

Colligative Properties A property that depends on the number of solute particles but is independent of their nature. 3 Colligative Properties: Vapor Pressure Lowering Freezing Point Depression 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