Properties of Solutions: Most things in life are solutions. Get with the program. Do Now: Clear desk except for a writing utensil- Intermolecular Forces Quiz Define the following words with a neighbor: Solvent: Solute: Aqueous solution: Entropy: Spontaneous: Predict the resulting reaction for Ammonium Nitrate and Water Do we expect this process to be endothermic or exothermic? Why? Why is this reaction surprising? What can we ask for the aim today? How is the ability of a substance to form a solution affected? Types of I.M.F in solution process Natural tendency of substances to mix/spread when not restrained Why is the mixing of gases a spontaneous process? No energy input from outside the system Why is it important to discuss entropy in solution? Increase in entropy is favored in solutions Explain why NaCl mixes in water and not gasoline. Three types of intermolecular attraction in solution formation: Solute-solute: interactions between molecules of solute must be overcome to disperse solute Solvent-solvent: interactions between solvent molecules must be overcome to make way for solute Solvent-solute: occur as particles mix In terms of intermolecular attraction, what must be true in order for a solution to form? In terms of intermolecular attractions, explain why heptane and pentane can mix. Write a paragraph explaining why NaCl is able to dissolve in water. Include the following terms: Solvent-solute Solute-solute Solvent-solvent Ion-dipole attraction Define: Solvation: Hydration: As we experienced in our demo, solution processes generally are accompanied by: How might we be able to determine how the interactions in the solution influence enthalpy? Formulate an equation to calculate ∆Hsoln Do Now: Write a paragraph explaining why NaCl is able to dissolve in water. Include the following terms: Solvent-solute Solute-solute Solvent-solvent Ion-dipole attraction Predict for each of the three types of interactions whether or not they are endothermic or exothermic. Explain your reasoning. Why is enthalpy useful to us in determining extent of reaction? How is forming a solution different than a chemical reaction? Define dissolution: What does this suggest for our aim? On the molecular level, explain the interactions of solute and solvent as concentration increases. Define the following terms with a neighbor: Saturation: Unsaturated: Supersaturation: Solubility How does solubility of gas relate to intermolecular forces? How do we differentiate between miscible and immiscible? How can we alter hexane to make is miscible? Explain in terms of attraction. **Hint: how does the number of carbons affect solubility in water? DO NOW: Predict whether each of the following substances is more likely to dissolve in the solvent carbon tetrachloride or water: C7H16 Na2SO4 HCl I2 Arrange the following in order of increasing solubility in water (explain your reasoning *psst.. Please actually write the reason in your notebook.**): c5H11OH, c5H12, c5H11Cl, c5H10(OH)2 As the world is evolving, the number of habitable lakes for wildlife is slowly declining. Predict the trend between pressure and solubility. Can you think of an example? At equilibrium, rate of gas molecules entering and leaving solution is equal. Exert pressure: what happens to the rate at which molecules are colliding with the surface? How can we relate this to the partial pressure of gas? Solubility of gas in a liquid solvent increases in direct proportion to partial pressure of gas. Relationship between pressure and gas solubility: Sg = kPg Sg= solubility of the gas in the solvent (usually expressed as molarity) Pg= partial pressure of the gas over solution k= proportionality constant (Henry’s Law Constant) **k depends on solute, solvent, and temp. Calculate the concentration of CO2 in a soft drink that is bottled with a partial pressure of 4.0 atm over the liquid at 25 degrees celcius. The Henry’s law constant for CO2 in water at this temperature is 3.4 x 10-2 mol/L-atm As temperature increases, the solubility of most solid solutes increases. How do you think gas solubility is effected by temperature? Why do bubbles form on the inside of the cooking pot when water is heated on a stove, even though the water temperature is well below the boiling point? How can we differentiate between mass percentage, ppm, and ppb? When would we use ppm or ppb? IE: toxic concentrations expressed in ppm or ppb: Max allowable concentration of arsenic in drinking water is 0.010 ppm. How do we express this in grams? A solution is made by dissolving 13.5 g of glucose in 0.100 kg of water. What is the mass percentage of solute in this solution? A 2.5 gram sample of groundwater was found to contain 5.4 microliters of zinc 2+. What is the concentration of Zn 2+ in ppm? Do Now: Calculate the mass percentage of NaCl in a solution containing 1.50 g of NaCl in 50.0 g of H2O. A commercial bleaching solution contains 3.62% by mass sodium hypochlorite (NaOCl). What is the mass of NaOCl in 2.50 kg of bleaching solution? 3.0 Molar 3.0 Molal How do we express mole fractions? IE: Solution contains 1.00 mol of HCl + 8.00 mol of H2O. What is the mole fraction of HCl? How do we express Molarity? IE: What is the molarity of a solution with 0.50 mol of solute in 0.250 L solution? How do we express molality? IE: 0.200 mols of NaOH is mixed with 0.500 kg of H2O. What is the concentration? How can we differentiate between molality and molarity? **Note: when water is solvent, the 2 numbers will be very similar. Why? Why do we use molality when varying temperature of solution? A solution is made by dissolving 4.35 g of glucose in 25 mL of H2O @ 25 degrees celcius. Calculate the molality. What is the molality of a solution made by dissolving 36.5 g of Naphthalene (C10H5) in 425 g of Toluene (c7H8)? Sometimes it is necessary to interconvert units when given a different unit. IE: An aqueous solution of HCl contains 36% HCl by mass. A solution with a denistry of 0.876 g/mL contains 5.0 g of Toluene and 225 g of Benzene. Calculate the molarity. Remember that worksheet you were given for homework? Time to go take another look at it… Do now: A solution containing equal masses of glycerol (C3H8O3) and water has a density of 1.10 g/ml. Calculate: ▪ The molality of glycerol ▪ The mole fraction of glycerol ▪ The molarity of glycerol Define Colligative Properties: Properties of solvents that depend on total concentration of solute particles present Give Examples of Colligative Properties: Vapor-Pressure Lowering Freezing Point Lowering Boiling Point Elevation Osmotic Pressure Redefine the following words in terms of vapor pressure: Vapor Pressure: Volatile: Non-volatile: Describe what would happen if you added a nonvolatile solute to a volatile solvent. Explain this visual. Vapor pressure of solution containing nonvolatile solue/volative solvent is proportional to solvent concentration How do we express this qualitatively? IE: Vapor pressure of water @ 20 degrees Celsius is 17.5 torr. If temp is held constant and sugar is added, mol fraction of water is XH2O= 8.00. How does the addition of glucose effect the vapor pressure? Glycerine- a nonvolatile nonelectrolyte with a density of 1.26 g/ml is used to make a solution with 50.0 mL glycerine with 500.0 mL water. At 25 degrees Celsius, the vapor pressure of water is 23.8 torr and density is 1.00 g/ml. The vapor pressure of pure water at 110 degrees Celsius is 1070 torr. A solution of ethylene glycol and water has a vapor pressure of 1.00 atm at 110 degrees Celsius. What is the mole fraction of ethylene glycol? Do Now: Calculate the Vapor Pressure of water above a solution prepared by adding 22.5 g of lactose (C12H22O11) to 200.0 g of water at 338 K. (pure water = 187.5 torr) Calculate the mass of propylene glycol (C3H8O2) that must be added to 0.340 kg of water to reduce the vapor pressure by 2.88 torr at 40 degrees Celsius. (pure water = 55.3 torr) Using prior knowledge, how might we relate the concept of an ideal gas to that of an ideal solution? Explain what this means for solute-solute, solvent-solvent, and solute-solvent interactions. ** Be aware, not all solutions are “ideal” will be discussed in later chapters. If the addition of non-volatile solute lowers vapor pressure, how is the boiling point effected? How can we represent the increase in boiling point numerically? IE: NaCl is dissolved in water. A 1 molal solution is created. Calculate the boiling point elevation of the solution. Summarize: A solute dissolved in water causes the boiling point to increase by 0.51 degrees celsius. Does this necessarily mean that the concentration of the solute is 1.0 m? Explain. How do we determine the freezing point of a liquid? How is freezing point effected when creating solutions? Explain. How might we calculate the change in freezing point? IE: Automotive antifreeze consists of ethylene glycol, CH2(OH)CH2(OH), a nonvolatile nonelectrolyte. Calculate the boiling point and greezing point of a 25.0 mass % solution of ethylene glycol in water. (Kb= 0.51 C/m) (Kf= 1.86 C/m) Which of the following solutes will produce the largest increase in boiling point upon addition to 1 kg of water and why Co(NO3)2 2 mol of KCl 3 mol of ethylene glycol (C2H6O2) Define semipermeable Define Osmosis Why does osmosis take place? *note: rate at which solvent passes from less concentrated solution (lower solute, higher solvent) to more concentrated solution is greater than the rate in the opposite direction Define Osmotic Pressure: Similar to ideal gas law: ∏ = (n/V)RT ∏ = osmotic pressure V= volume of the solution n= number of moles of solute R = ideal gas constant T = temperature in Kelvin How can we change the equation to include Molarity? Using these diagrams and the concept of osmotic pressure, label and define which of these are isotonic, hypotonic, and hypertonic. Describe what would happen if a red blood cell was placed in a solution that is hypertonic relative to the intracellular solution. Crenation: process in which a cell shrivels Describe what would happen if the cell is hypotonic relative to intracellular fluids. Hemolysis: process of cell repture The average osmotic pressure of blood is 7.7 atm @ 25 degrees celsius. What molarity of glucose will be isotonic with blood? What is the osmotic pressure at 20 degrees Celsius of a 0.0020 M sucrose solution? (C12H22O11) Any of the four colligative properties can be used to determine molar mass: 1. Freezing Point Depression/ Boiling Point Elevation: ▪ A solution of unknown solute was prepared by dissolving 0.250 g of the substance in 40.0 g of CCl4. The resultant boiling point of the solution was 0.357 degrees higher than that of the pure solvent. Calculate the molar mass. Osmotic Pressure: The osmotic pressure of an aqueous solution of a certain protein was measured to determine the proteins molar mass. The solution contained 3.50 mg of protein dissolved in sufficient water to form 5.00 mL of solution. The osmotic pressure of the solution at 25 degrees celsius was found to be 1.54 torr. Calculate the molar mass. Camphor (C10H16O) melts at 179.8 degrees Celsius and it has a large Kf= 40.0 C/m. When 0.186 g of an organic substance of unknown molar mass is dissolved in 22.01 g of liquid camphor, the freezing point is found to be 176.7. What is the molar mass? A sample of 2.05 g of polystyrene of uniform polymer chain length was dissolved in enough toluene to form 0.100 L of solution. The osmotic pressure of the solution was found to be 1.21 kPa at 25 degrees Celsius. Calculate the molar mass.