CHEM 102 1nd Edition Lecture 4 Outline of Current Lecture I. Concentration and Freezing PointII. Boiling Point and Freezing PointIII. Osmotic PressureCurrent LectureI. Concentration and Freezing Point- Freezing Point Depression: the freezing point is lowered with increasing concentration in the solution- ΔT = kfmo ΔT is the change in temperature to the freezing pointo m is molalityo kf is a constant specific for the solvent- Example: What is the freezing point of a 0.030 molality solution?o Where, kf of H2O is 1.86o ΔT = kfmo ΔT = 1.86 x 0.030 = 0.0558o So, the freezing point of water is 0o 0 – 0.0558 = - 0.0558- ΔT is subtracted from the normal freezing temperature to determine the new freezing temperature of the solutionII. Boiling Point and Freezing Point- The solute interferes with the boiling of a solvent, so the boiling point is raised in the solution relative to the original solvent- ΔT = kbmo ΔT is the change in temperature to the boiling pointo m is molality o kb is the constant specific to the solvent- ΔT is added to the normal boiling point because the boiling point in the solution is elevatedIII. Osmotic Pressure- Osmosis needs something semi-permeable for the solvent to travel through- Isotonic means the net flow is 0, equilibriumThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Hypotonic means the net flow is into the solution because the surroundings has a lower concentration that that of the solution.- Hypertonic means the net flow is out of the solution because the surroundings has a higher concentration than that of the solution.o Way to remember: a HYPER active child acts OUT- Osmotic pressure is represented by π. o Osmotic pressure is the difference in height when osmosis occurs.o Or osmotic pressure is the amount of pressure needed to stop the flow ofosmosis from one side of the semi-permeable barrier to the other sideo Or the external pressure needed to prevent an increase in volume. o In the picture, the picture on the left is when the solutions were added in the beginningo The picture on the right is how the solutions look after osmosis has occurred and off balanced the solutions, the differences are marked with π- π = MRTo M is the molarity o R is a constant, 0.0821 l ∙ atmmol ∙ Ko T is the temperature in
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