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Formation of a solution • The composition of the solute and solvent will determine whether a substance will dissolve.
Stirring (agitation), temperature, and the surface area of the solutes determine how fast the substance will dissolve.
Solubility How well a solute can dissolve in a solvent. • Saturated solution Contains the maximum amount of solute possible for a given temperature and pressure.
Unsaturated Solution More solute can be squeezed into the solution. • Miscible Two liquids can be mixed • Immiscible Two liquids that don’t mix.
Temp affects the solubility of solid, liquids and gases. Both Temp and Pressure affect the solubility of gases.
Supersaturated solution Contains more solute than allowed at that temperature.
Solubility for gases S1/P1 = S2/P2 Unit of solubility is g/L, pressure is atm
If there are 5 mols of NaCl in 20 liters of water, what is molarity of the NaCl solution? • .25 M
Making Dilutions M1*V1 = M2 * V2
You have a 1 M NaCl solution. How can you make 10 Liters of a .5 M solution? • Use 5 liters of 1M solution, then fill to 10 L with water.
Percent concentration volume/volume • Volume solute/ total volume * 100%
Percent concentration (mass/mass) Mass solute/mass solution * 100%
What is the Molarity of a .9 g / 100 mL solution of NaCl (58.5 = molar mass)? • .15 M
NOTES 2 • Colligative Properties: Depend only on the number of solute particles.
Vapor-pressure lowering: Solutes will lower the vapor pressure. • Solute molecules “trap” solvent molecules. This makes it more difficult for the solvent molecules to evaporate.
Draw this • What will produce the greatest lowering in vapor pressure, 3 mols of glucose, 3 mols of NaCl, or 3 mols of CaCl2?
Freezing point depression The more solutes in a solution, the lower its freezing/melting point.
The more solute molecules a solution has, the more difficult it is to compact together and freeze.
Which will have the lowest freezing point? 3 M NaCl, 3 M PCl3
Boiling point elevation Solutes get in the way of solvent molecules and make it harder for them to evaporate away.
Mole Fraction • Mols of one thing divided by Total mols of everything. • What is the mol fraction of NaCl if it is in a solution that contains 2 mol NaCl, 2 mol of LiBr, and 6 mol of H2O? • .2
∆Tf = Kf * m (FP depression) • Kf = Molal freezing-point depression constant • ∆Tb = Kb * m (BP Elevation) • Kb = Molal boiling-point elevation constant
What is the freezing point depression and the new freezing point of a solution that has 1.61 mols of C2H6O2 antifreeze in .5 kg of water? • 1.86 * 3.22 = 5.99 • -5.99 C is new freezing point
Partner Review Activity: • Page 499, #42, 51