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##### Ch. 16 Solutions

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**Solutions are homogeneous mixtures that may be solid, liquid**or gas.**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.**What is the Molality? 2 mols of NaCl, 4 kg of water.**• .5 molal**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