Solutions Homogeneous Mixtures Solutions: Mixtures that contain two or more substances called the solute and the solvent where the solute dissolves in the solvent so the solute and solvent are not distinguishable (I.E. salt water or sugar water) Soluble: A solute that dissolves in a specific solvent Insoluble: A solute that will not dissolve in a specific solvent "Like Dissolves Like" Mar 19 1:29 PM Molarity Molarity is a form of concentration (a value that describes how much solute there is per solution) Remember that an aqueous solution is a solute dissolved in water. (This is the main type of solution we will work with in this class) Molarity (M) = Moles of solute liters of solution Mar 16 8:34 AM 1
Molarity So let's say we have a solution that is made from adding 45.6 grams of sodium chloride in 378 ml water. What is the molarity of the solution? Step 1: Change grams into moles 45.6g NaCl 1 mol NaCl 58g NaCl = 0.786 mol NaCl Step 2: change your volume into liters 378 ml 1 L 1000 ml = 0.378 L Step 3: divide your number of moles by the volume of the solution 0.786 mols NaCl 0.378 L = 2.08 M Mar 16 8:34 AM Molarity 121.4 grams of potassium oxide is dissolved in 134.5mL of water. what is the molarity of the solution? Mar 16 8:35 AM 2
Dilutions M 1 V 1 = M 2 V 2 You want to make 500 ml a 0.25M solution of HCl, and you have a 1.50M solution of HCl available. How much of the 1.50M solution of HCl will you need to use? (0.25M)(500mL) = (1.50M)(V 2 ) V 2 = 83.3 ml You will need 83.3 ml of the original 1.50M solution of HCl Mar 19 2:02 PM Molality Molality: Moles of solute per kilogram of solvent symbolized by a m m = mols solute kg of solvent Find the molality of a solution where 25.6 grams of Lithium nitrate is added to 500.0 grams of water Mar 23 8:27 AM 3
States of Matter Phase Changes liquid Freezing Melting Solid Deposition Vaporization Condensation Sublimation Gas Mar 18 9:44 AM States of Matter Phase Diagram: A graph of pressure versus temperature that shows in which phase a substance exists under different conditions of temperature and pressure. Triple point: the pressure at which all three phases of a substance can coexist all 6 phase changes are possible at this point Critical point: The point that indicates the critical pressure and critical temperature above which water cannot exist as a liquid Normal Boiling or Normal Freezing Point: is the temperature at 1 atm where water boils or freezes Mar 18 9:46 AM 4
States of Matter : properties of solutions that depend upon the ratio of the number of solute particles to the number of solvent molecules in a solution The more ions produced from the solute, the more affect the solute will have on the property Boiling Point Elevation: By adding a solute to pure water, the water must be heated to a higher temperature than the 100C. Reasoning: the solute will form new intermolecular bonds with the solvent meaning that the solution will not have as high of a vapor pressure as the pure water, this means that have the vapor pressure reach the atmospheric pressure more energy must be added by raising the temperature Freezing Point Depression: By adding a solute to pure water, the water must be cooled to a lower temperature than the 0C. Reasoning: the water must have a certain order to its intermolecular bonds to be able to freeze; a solute will break up these intermolecular bonds to make its own with the solvent, so to reach a point where the right intermolecular bonds will form the water must be cooled to a lower temperature. Mar 19 2:25 PM Phase Diagrams with Mar 18 9:47 AM 5
Boiling Point Elevation Boiling point is elevated compared to the pure solvent Change in boiling point ΔT b = ik b m solute Molal boiling point elevation constant For Water: K b = 0.51 /m Molality of the solute in the solution Mar 23 7:59 AM Boiling Point Elevation ΔT b = ik b m solute K b = 0.51 /m A solution was prepared by dissolving 18.00g glucose in 150.0g water. Calculate the new boiling point of the solution. Remember: Glucose is a covalent compound so it is only 1 particle. Mar 23 8:08 AM 6
Boiling Point Elevation ΔT b = ik b m solute K b = 0.51 /m A solution was prepared by dissolving 79.0 g calcium chloride in 500.0g of water. Calculate the new boiling point of the solution. Remember: calculate the number of ions by writing out the compound first. Mar 23 8:08 AM Freezing Point Depression This freezing point is lower than the original freezing point Change in freezing point ΔT f = ik f m solute Molality of the solute in the solution Molal freezing point depression constant For Water: K f = 1.86 /m Mar 23 8:12 AM 7
Freezing Point Depression ΔT f = ik f m solute K f = 1.86 /m What is the freezing point of a solution where 12.5 grams of Ethylene glycol (C 2 H 6 O 2 ) is added to 1000 grams of water to produce a solution for use in a car's radiator. (Ethylene glycol is a covalent compound) Mar 23 8:14 AM Freezing Point Depression ΔT f = ik f m solute K f = 1.86 /m What is the freezing point of a solution where 143 grams of aluminum sulfate is added to 550 grams of water. (determine the ions before starting the math) Mar 23 8:14 AM 8
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