When will solute and solvent create a solution? Think about the Chromatography Lab! ” Like dissolves like”  H solution =  H 1 +  H 2 +  H 3 What happens if…  H 1(solv)  H 2 (solute) H3H3  H solution Outcome? Polar solvent and solute Nonpolar solvent and solute Polar solvent and nonpolar solute Nonpolar solvent and polar solute

Why do solutions form if  H is positive? When a salt dissociates, the energy associated with the separation of ions(lattice energy) is often so large resulting in an endothermic  Hsoln Coulomb’s Law: F = q1q2/r2 If ions are highly charge, soluble or insoluble?

What factors effect solubility? Pressure (for gas solute only) Henry’s Law C= kP The elevation of Lake Havasu is 400 feet, and Lake Tahoe is 6200 feet. If the water temperatures are the same, which lake has a lower concentration of oxygen gas? For aqueous solutions, temperature … Many solids increase in solublity as temperature increases, some don’t Gases Are less soluble as temperature increases, why?

In our BORAX crystal experiment we relied on solubility. What does it measure? amount of solute dissolved in a given amount of solvent – typically measured in g solute/100 g solvent Saturated Unsaturated Supersaturated

Do Now: What is vapor pressure? What factors impact it? What are colligative properties? What will happen over time in the picture? Water Aq. soln Closed environment

Colligative properties? Properties of a solution that depends on the number of particles in a given volume of solvent and not on the mass of the particles. Physically we apply this principle at home. In the laboratory, this is a means to accurately determine the molar mass of a solute.

The addition of a nonvolatile solute (right) decreases the number of solvent molecules per unit volume and lowers solvent’s escaping tendency, thereby lowering vapor pressure Compare the pure solvent and solution depicted below

Vapor Pressure Reduction Raoult’s Law P solution = x solvent P solvent (nonvolatile solute) X is mole fraction What if the solute is volatile? P solution = x solvent P solvent + x solute P solute Applies to an ideal solution

TRY WITHOUT CALCULATOR! A solution is prepared by mixing 5.81 g acetone (C 3 H 6 O, molar mass = 58.1 g/mol) and 11.9 g chloroform (HCCl 3, molar mass = g/mol). At 35°C, this solution has a total vapor pressure of 260. torr. Is this an ideal solution? Explain why or why not. The vapor pressures of pure acetone and pure chloroform at 35°C are 345 and 293 torr, respectively.

How does the freezing point and boiling point of a solution compare to the pure solvent? Explain at molecular level. Remember … 1. at phase change equilibrium is established 2. boiling/freezing point are temperatures when the vapor pressure of the solid (fp) or liquid(bp) are equal to the external atmospheric pressure.

Boiling Point Elevation Freezing Point Depression  T b = i k b m  T f = i k f m

The molar mass of an unknown hydrocarbon is determined by dissolving in CHCl 3. The solution is prepared by mixing 100. grams of CHCl 3 and gram of the hydrocarbon is °C. The molal freezing-point depression constant of CHCl 3 is 4.68 °C / molal and its normal freezing point is °C. Calculate the molecular weight of the hydrocarbon.

What is osmosis? Osmosis is the spontaneous movement of solvent molecules through a semi-permeable membrane from an area of higher solvent concentration to an area of lower solvent concentration. SolutionPure Solvent SolutionPure Solvent Semipermeable membrane Osmotic pressure

Osmotic Pressure  = iMRT What concentration of sodium chloride in water is needed to produce an aqueous solution isotonic with blood (π= 7.70 atm at 25°C)? What would happen if a pressure that exceeded osmotic pressure was applied to the solution?

Osmotic Pressure - SomeApplications Water Purification (Reverse Osmosis) Physiology Water Transport in Plants (Osmosis pushes, hydrogen bonding pulls) Food Preservation (salty,sugary)

Van’t Hoff Factor, i What is it? What is ion pairing? What is the effect of concentration?

Formulas: Mass % = mass A/ total mass x 100 Molarity = moles solute/L solution Molality = moles solute/kg solvent Mole fraction = moles A/ total moles Psolution = xsolventPsolvent + xsolutePsolute  T = ikm  = iMRT

DO NOW! In preparing a solution … are moles conserved? is volume conserved? is mass conserved?

What is a colloid? 1. Solution 2. Colloid 3. Suspension = Particle Size < 1 nm 1 – 100 nm > 100 nm

Solution Does not settle, passes through filter paper, does not scatter light Colloid Does not settle, passes through filter paper, will scatter light Suspension Will settle on standing, separated by filter paper, will scatter light Tyndall effect - effect of light scattering on particles in colloid systems

Some colloids- Classification of Colloids:- Jello (Liquid dispersed phase in solid medium) Aerosol sprays (Liquid dispersed phase in gaseous medium) Whipped Cream (Gaseous dispersed phase in liquid medium) Mayonnaise (Liquid dispersed phase in liquid medium)

Medium / Phases Dispersed phase GasLiquidSolid Gas All gases are miscible in each other so no colloid Liquid Aerosols. Ex- Fog, Mist, Hair sprays. Solid Aerosols Ex- Smoke, Clouds, Air Particles. Liquid Foam Ex- whipped cream, Shaving cream Emulsions Ex- Mayonnaise, Milk, Hand creams. Sol Ex- Blood and pigmented ink, Milk of magnesia. Solid Solid foam Ex- Pumice stone, Styrofoam Gel. Ex- Gelatin, Jams, Jellies, Jello Solid Sol Ex- Metals alloys, Pearl Classification of Colloids:-