Solutions Chapter 13 & 14

Solution  A uniform mixture that may contain solids, liquids, or gases  Also called a homogeneous mixture  Composed of a solute & solvent Solute: substance that dissolves Solute: substance that dissolves Solvent: dissolving medium Solvent: dissolving medium The most common solvent is water. SOLUTE + SOLVENT  SOLUTION

Solubility  The maximum amount of solute that will dissolve in a given amount of solvent  Solubility INCREASES as temp increases  Solubility DECREASES as pressure increases  Solubility INCREASES as surface area increases

Solutions…  Saturated solution: contains the maximum amount of dissolved solute for a given amount of solvent  Unsaturated solution: contains less dissolved solute than a saturated solution  Supersaturated solution: contains more dissolved solute than a saturated solution

A substance that dissolves in a substance is soluble. Ex. Sugar is soluble in water A substance that does not dissolve in a solvent is insoluble. Ex. Sand is insoluble in water

Two liquids that are soluble in each other are miscible. Ex. Water & acetic acid are miscible Two liquids that are insoluble in each other are immiscible. Ex. Oil & vinegar are immiscible

Concentration: a measure of how much solute is dissolved in a solution Concentrated solution: contains a large amount of solute Dilute solution: contains a small amount of solute

Expressing Concentration  Some common ways to express concentration are: Percent by mass Percent by mass Percent by volume Percent by volume Molarity Molarity Molality Molality

Percent by mass  Describes solutions in which a solid is dissolved in a liquid % by mass= mass of solute x 100 mass of solution mass of solution Mass of solution= mass of solute + mass of solvent Mass of solution= mass of solute + mass of solvent

Percent by volume  Describes solutions in which both solute & solvent are liquids % by volume= volume of solute x 100 % by volume= volume of solute x 100 volume of solution volume of solution

Problem Find the percent by mass of a solution containing 50g of NaCl dissolved in 100g of water.

Molarity Molarity (M)= moles of solute Molarity (M)= moles of solute liter of solution liter of solution

Problem You have 3.50L of solution that contains 90.0g of sodium chloride, NaCl. What is the molarity of the solution?

Dilution  A concentrated solution can be diluted by adding more solvent to the solution. M 1 V 1 = M 2 V 2 M 1 V 1 = M 2 V 2

Problem What volume is needed to dilute 3L of a 12M HCl solution to 2M HCl?

Molality Molality (m)= moles of solute Molality (m)= moles of solute kg of solvent kg of solvent

Problem A solution was prepared by dissolving 17.1g of sucrose (table sugar, C 12 H 22 O 11 ) in 125g of water. Find the molality of this solution.

Colligative properties  Solutes affect some of the physical properties of their solvents. These properties are called colligative properties. Adding a solute to a solvent LOWERS the vapor pressure. Adding a solute to a solvent LOWERS the vapor pressure. Adding a solute to a solvent RAISES the boiling point. Adding a solute to a solvent RAISES the boiling point. Adding a solute to a solvent LOWERS the freezing point. Adding a solute to a solvent LOWERS the freezing point.