Due: Formal Lab Report – Chemical Equilibrium Docked a full letter grade for being late Today: 1. Electrolytes 2. Properties of Solutions 3. Solubility Product Constant Ksp HW: Ksp Worksheet

Classification of Matter Solutions 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

“Like Dissolves Like” Fats 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

Water’s Solvent Interactions Water’s Solvent Interactions The oxygen (slightly negative) end of the water molecule is attracted to the positive ion of a salt.

Water’s Solvent Interactions The hydrogen (slightly positive) end of the water molecule is attracted to the negative ion of a salt.

Does everything dissolve? How do we know when substances have dissolved? What are the indicators? When a substance dissolves in a solvent how does it affect the properties?

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

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 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 Try to classify the following substances as electrolytes or nonelectrolytes…

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

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. Definition of Electrolytes and Nonelectrolytes

Salts What is a salt? Do all salts dissolve equally? Salts are ionically bonded substances (electrolytes) that have a pH of 7 How can we measure how well a salt dissolves?

Do all salts dissolve the same? Since these systems are in equilibrium we can compare the relationship between he solid solute and the aqueous ions NaCl (s)  Na + (aq) + Cl - (aq) PbSO 4 (s)  Pb + (aq) + SO 4 2- (aq)

Equilibrium Constant NaCl (s)  Na + (aq) + Cl - (aq) PbSO 4 (s)  Pb + (aq) + SO 4 2- (aq) Ksp = 37.3 Ksp = 1.82 x 10.8

Solubility Product Constant - Ksp

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

Solubility Chart

Precipitating Some ionic compounds are insoluble and will form a precipitate (ppt) Ex: Ag + (aq) + Cl - (aq) → AgCl (s) PbI White ppt Barium chromate

Solubility Chart Rules Ex: Barium nitrate and sodium sulfate react

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. Each mole of nonvolatile solute particles raises the boiling point of 1 kilogram of water by 0.51 degrees Celsius. Boiling Point Elevation