Classification of Matter Solutions are homogeneous mixtures

Solute A solute is the dissolved substance in a solution. A solvent is the dissolving medium in a solution. Solvent Salt in salt water Sugar in soda drinks Carbon dioxide in soda drinks Water in salt waterWater in soda

Aqueous solutions Dissolved in water. Water is a good solvent because the molecules are polar. The oxygen atoms have a partial negative charge. The hydrogen atoms have a partial positive charge. The angle is 105º

Alloys Solid solutions of one metal evenly dissolved in another. Examples: brass and bronze

Dissolution of sodium Chloride

Steps in Solution Formation  H 1 Expanding the solute  H 2 Expanding the solvent  H 3 Interaction of solute and solvent to form the solution Separating the solute into individual components Overcoming intermolecular forces of the solvent molecules

Concentrated vs. Dilute

Heat of Solution The Heat of Solution is the amount of heat energy absorbed (endothermic) or released (exothermic) when a specific amount of solute dissolves in a solvent. Substance Heat of Solution (kJ/mol) NaOH NH 4 NO KNO HCl-74.84

The ammeter measures the flow of electrons (current) through the circuit.  If the ammeter measures a current, and the bulb glows, then the solution conducts.  If the ammeter fails to measure a current, and the bulb does not glow, the solution is non-conducting. Electrolytes vs. Nonelectrolytes

An electrolyte is: A substance whose aqueous solution conducts an electric current. A nonelectrolyte is: A substance whose aqueous solution does not conduct an electric current. Try to classify the following substances as electrolytes or nonelectrolytes… Definition of Electrolytes and Nonelectrolytes

1.Pure water 2.Tap water 3.Sugar solution 4.Sodium chloride solution 5.Hydrochloric acid solution 6.Lactic acid solution 7.Ethyl alcohol solution 8.Pure sodium chloride Electrolytes?

ELECTROLYTES:NONELECTROLYTES: Tap water (weak) NaCl solution HCl solution Lactate solution (weak) Pure water Sugar solution Ethanol solution Pure NaCl Answers to Electrolytes

Calculations of Solution Concentration Mass percent - the ratio of mass units of solute to mass units of solution, expressed as a percent

Calculations of Solution Concentration Molality – moles of solute per kilogram of solvent

Calculations of Solution Concentration Molarity - the ratio of moles of solute to liters of solution

“Like Dissolves Like” Fats Benzene Benzene Steroids Steroids Hexane Hexane Waxes Waxes Toluene Toluene Polar and ionic solutes dissolve best in polar solvents Nonpolar solutes dissolve best in nonpolar solvents Inorganic Salts Water Water Sugars Sugars Small alcohols Small alcohols Acetic acid Acetic acid

Solubility Trends  The solubility of MOST solids increases with temperature.  The rate at which solids dissolve increases with increasing surface area of the solid.  The solubility of gases decreases with increases in temperature.  The solubility of gases increases with the pressure above the solution.

Therefore… Solids tend to dissolve best when: o Heated o Stirred o Ground into small particles Gases tend to dissolve best when: o The solution is cold o Pressure is high

Saturation of Solutions  A solution that contains the maximum amount of solute that may be dissolved under existing conditions is saturated.  A solution that contains less solute than a saturated solution under existing conditions is unsaturated.  A solution that contains more dissolved solute than a saturated solution under the same conditions is supersaturated.

Solubility Chart

Henry’s Law The concentration of a dissolved gas in a solution is directly proportional to the pressure of the gas above the solution Applies most accurately for dilute solutions of gases that do not dissociate or react with the solvent Yes  CO 2, N 2, O 2 No  HCl, HI

Calculations of Solution Concentration Mole fraction – the ratio of moles of solute to total moles of solution

Calculations of Solution Concentration Concentration - A measure of the amount of solute in a given amount of solvent or solution Molarity - moles of solute divided by the volume of solution in liters Parts per million – the ratio of parts (mass) of solute to one million parts (mass) of solution Grams per liter - the mass of solute divided by the volume of solution, in liters Percent composition - the ratio of one part of solute to one hundred parts of solution, expressed as a percent

What is a possible explanation for the wood frog’s ability to survive being frozen?

Colligative Properties Colligative properties are those that depend on the concentration of particles in a solution, not upon the identity of those particles.  Boiling Point Elevation  Freezing Point Depression  Osmotic Pressure

Freezing Point Depression Each mole of solute particles lowers the freezing point of 1 kilogram of water by 1.86 degrees Celsius. K f = 1.86  C  kilogram/mol m = molality of the solution van’t Hoff i = van’t Hoff factor Freezing Point Depression Each mole of solute particles lowers the freezing point of 1 kilogram of water by 1.86 degrees Celsius. K f = 1.86  C  kilogram/mol m = molality of the solution van’t Hoff i = van’t Hoff factor

Boiling Point Elevation Each mole of solute particles raises the boiling point of 1 kilogram of water by 0.51 degrees Celsius. K b = 0.51  C  kilogram/mol m = molality of the solution van’t Hoff i = van’t Hoff factor

Freezing Point Depression and Boiling Point Elevation Constants,  C/ m SolventKfKf KbKb Acetic acid Benzene Nitrobenzene Phenol Water

The van’t Hoff Factor, i Electrolytes may have two, three or more times the effect on boiling point, freezing point, and osmotic pressure, depending on its dissociation.

Dissociation Equations and the Determination of i NaCl(s)  AgNO 3 (s)  MgCl 2 (s)  Na 2 SO 4 (s)  AlCl 3 (s)  Na + (aq) + Cl - (aq) Ag + (aq) + NO 3 - (aq) Mg 2+ (aq) + 2 Cl - (aq) 2 Na + (aq) + SO 4 2- (aq) Al 3+ (aq) + 3 Cl - (aq) i = 2 i = 3 i = 4

Osmotic Pressure Calculations  = Osmotic pressure M = Molarity of the solution R = Gas Constant = L  atm/mol  K i = van’t Hoff factor