CHEM 1032 Lecture Notes - Lecture 7: Colligative Properties, Intermolecular Force, Freezing-Point Depression

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scarletmoose272

4 Feb 2017

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Colligative properties with respect to nonelectrolytes: vapor pressure lowering, boiling point elevation, freezing point depression, osmotic pressure. Since condensation is occurring faster than vaporization the concentration of gas will decrease. Vapor pressure will also lower: rault"s law: For a volatile solute, solute and solvent would have their own vapor pressure: vapor pressure lowering occurs at all temperatures. Boiling point elevation: pvap is lower due to a solute being present. Will require more energy put in to get to the boiling point. Freezing point depression: entropy is decreasing as this occurs. Lower and lower temperature is why freezing point is depressed: t = (m)(kf, avoid making solution into a solid because of higher energy needed, solute is incorporated into the solid. Osmotic pressure: osmosis: the flow of solvent from a solution of lower solute concentration to an area of higher solute concentration, semipermeable membrane: allows only certain things to cross. Two sides are getting closer to equal concentration.

Related Questions

DETERMINATION oF MOLAR EXPERIMENT 23 MASS FROM FREEZING POINT DEPRESSION EQUIPMENT AND CHEMICALS: Equipment 600 mL beaker Chemicals Cyclohexane (C Stir plate 100 ml. graduated cylinder Clamp Nonvolatile Unknowns Freezing point apparatus Spin vane 0.1 C Thermometer INTRODUCTION: When a solute is introduced into a pure solvent the newly formed solution will have certain physical properties that are from the solvent. As a of the presence of the the pressure of the solution will be lower than that of the pure solvent. As the vapor pressure is lowered there is a resulting increase in the amount of energy required to reach the boiling point of the solution. Conversely, the solution must cool to a lower temperature before a state change from liquid to solid occurs. These changes in physical properties vapor pressure lowering, boiling point elevation and freezing point depression are collectively referred to as colligative properties. These colligative properties, which also include osmotic pressure, do not depend on the nature of the nonvolatile solute in the solution but rather on the concentration of solute present. Because the properties are independent of the nature of the solute, they may be used to determine other properties of the solute such as molecular weight. The effect of a nonvolatile, nonelectrolyte solute on a pure solvent will be examined by finding the freezing point depression of a cyclohexane unknown so solution. The freezing point of a pure sample of cyclohexane will be determined. Introducing a nonelectrolyte solute should in solution formed to freeze at a lower temperature. This temperature will then be experimentally determined As stated the The molality of the solution dependent on the quantity of solute particles present in solution. (moles solute particles per kilogram of solvent) is directly proportional to the change in temperature between the freezing point of the pure solvent and that of the ATfss Kim The molal freezing point depression constant, K for cyclohexane is equal to 20.00 cfmolal By experimentally determining the freezing point depression of a ohexanel unknown solution, the molal concentration is easily calculated. In turn the molar mass of the unknown olute can be calculated as well Chemistry 132 EXPERIMENT23

Vapor-pressure lowering is a colligative property, as are freezing-point depression and boiling-point elevation. What is a colligative property? Why is the freezing point depressed for a solution as compared to the pure solvent? Why is the boiling point elevated for a solution as compared to the pure solvent? Explain how to calculate ∆T for a freezing-point depression problem or a boiling-point elevation problem. Of the solvents, which would have the largest freezing-point depression for a 0.50 molal solution? Which would have the smallest boiling-point elevation for a 0.50 molal solution? A common application of freezing-point depression and boiling-point elevation experiments is to provide a means to calculate the molar mass of a nonvolatile solute. What data are needed to calculate the molar mass of a nonvolatile solute? Explain how you would manipulate these data to calculate the molar mass of the nonvolatile solute.