Solutions and Solubility Chapters 15 and 16

Solution Homogeneous Mixture Aqueous Solution Uniform Throughout Something mixed in water NaCl(aq)

Solution Components Solvent Solute Dissolving medium in mixture Dissolved particles in solution

Solubility measure of the amount of solute that can dissolve in a given quantity of solvent at certain conditions How much can dissolve

Solubility Soluble Insoluble Solute will dissolve in solvent Solute will not dissolve in solvent

Factors that affect Solubility Temperature Pressure Type of Chemical

Temperature increasing temperature increases solubility of solids and liquids in other solids and liquids decreasing temperature increases solubility of gases in liquids Ex: Cold soda is fizzy

Pressure Increasing partial pressure of gas above liquid increases solubility of the gas in the liquid Example Soda Bottles

Type of Chemical “Like dissolves Like” Polar and ionic substances will dissolve in polar solvents Nonpolar substances will dissolve in nonpolar solvents

Solutions Concentrated Dilute General term for a lot of solute dissolved in solvent Dilute General term for not a lot of solute dissolved in solvent Opposite of concentrated

Table G Shows the relationship between temperature and amount of solute for a number of different compounds

Table G How much NaNO3 can dissolve in 100g of H2O at 50°C? 115g

Table G At what temperature can 60g of NH4Cl dissolve in 100g of H2O?

Types of Solution Saturated Unsaturated Supersaturated maximum amount of solute for a given quantity of solvent At Equilibrium Unsaturated contains less than the maximum amount of solute Supersaturated Contains more solute than it can theoretically hold

Supersaturated Solutions Begins as saturated solution at high temp As solution cools, with no disturbance, solubility decreases Any disturbance, or place for a crystal to grow, will cause any excess solute to precipitate out back to a saturated solution

Solution Types Saturated Unsaturated Supersaturated On the line Under the line Supersaturated Above the line

Electrolytes Compounds that conduct an electrical current when melted or dissolved Ionic compounds Including acids and bases NaCl, KNO3, HCl

Dissolving vs. Dissociation Molecules separate as solvent molecules mix C6H12O6(s) + H2O(l)  C6H12O6(aq) Dissociation Ions separate as solvent molecules mix NaCl(s) + H2O(l)  Na+(aq) + Cl-(aq)

Dissociation Simulation http://phet.colorado.edu/simulations/sims.php?sim=Salts_and_Solubility

Concentration Quantitative measure of the amount of solute dissolved in a given quantity of solvent Molarity Percent Composition by mass, by volume Parts Per Million (ppm)

Molarity Molarity = Moles of Solute Liters of Solution 1 mol/L = 1 M Often used for solids dissolved into liquids Most common concentration system

Molarity Example What is the molarity of 2 moles of glucose dissolved in 5 Liters of solution? Molarity = Moles of Solute Liters of Solution

Example How many moles of HCl are dissolved in 4L of a 3M solution of HCl? Molarity = Moles of Solute Liters of Solution

Example What volume of a 6M solution contains 0.6moles of NaCl? Molarity = Moles of Solute Liters of Solution

Percent Composition Percent Comp = Part x 100% Whole By mass %(m/m) Usually used for solid - solid solutions By Volume %(v/v) Usually used for liquid - liquid solutions

(v/v) Example A solution contains 60 mL of NH3 in a 1 Liter solution, what is the percent by volume composition of this solution?

Parts Per Million (ppm) Used for very small concentrations ppm = grams of solute x 1,000,000 grams of solution Units = ppm

ppm example A 2 kg bar of silver contains 0.05 g of gold, what is the parts per million concentration of gold in the silver bar? 25 ppm Au

Example A bar of tantalum has a niobium concentration of 16ppm. How much does the bar weigh if the niobium weighs 0.004g?

Colligative Properties of Solutions Properties of a solution that depend only on the number of particles dissolved Vapor Pressure Boiling Point Melting Point

Vapor Pressure Pressure exerted by a vapor that has evaporated and is still above a liquid More solute particles get in the way of solvent particles trying to evaporate Adding more nonvolatile solute particles to pure solvent decreases vapor pressure

Boiling Point Temperature at which a liquid boils at a given pressure, related to vapor pressure. More solute particles get in the way of solvent particles trying to escape liquid phase Adding more solute particles to pure solvent increases boiling point

Freezing Point Temperature at which a liquid freezes, or the particles line up in an orderly pattern. More solute particles get in the way of the solvent particles trying to line up. Adding more solute particles to pure solvent decreases freezing point

Number of Particles When a covalent compound dissolves the compound stays intact. When an ionic compound dissociates the compound splits into its ions.

Examples When glucose, C6H12O6, dissolves it will split into how many particles? 1, C6H12O6 When NaCl dissociates it will split into how many particles? 2, Na+ and Cl- When CaCl2 dissociates it will split into how many particles? 3, Ca2+, Cl-, and Cl-

Example For a solution of each glucose, NaCl, and CaCl2 Substance calculation Change in Temp Glucose (4M)(1particle) 4 NaCl (3M)(2particles) 6 CaCl2 (1M)(3particles) 3

Real Life Why do we put salt on roads in winter? Salt lowers freezing point, ice melts Which is better NaCl or CaCl2? CaCl2, more particles Why do some people use salt when cooking pasta? (Besides Taste) Raises boiling point, cooks at higher temperature