grams of solvent-
- Question 1 Pls Show All Work Grams Of Solvent Kf Delta T Question 2 Unknown Vanillin Grams Of Solvent 1 07g Gr 1 (27.56 KiB) Viewed 35 times
Delta T-
Question 2:
unknown- Vanillin
- Question 1 Pls Show All Work Grams Of Solvent Kf Delta T Question 2 Unknown Vanillin Grams Of Solvent 1 07g Gr 2 (27.56 KiB) Viewed 35 times
- Question 1 Pls Show All Work Grams Of Solvent Kf Delta T Question 2 Unknown Vanillin Grams Of Solvent 1 07g Gr 3 (77.17 KiB) Viewed 35 times
grams of solute- 8.25g
delta T- (-11.3)
LCULATIONS: Calculate the molar mass using the equations given in the introduction of this experiment. You will need the grams of solvent, grams of solute, Kr and AT. You will be given the name of the unknowns you use. Use a CRC Handbook or Merck Index to look up the Structure and the molar mass of your unknown. Use this value for determining percent error (list reference). Place your results and the average molar mass in a Report Table. Write both the molecular formula for the substance AND the complete structural formula below the report table.
DETERMI BY FREEZING POINT DEPRESSION INTRODUCTION: The freezing point depression of a solution is a common method for the determination of the molar mass of a solute. The freezing point depression is a colligative property of a solution, a property which ideally depends only on the number of moles of solute and not on the nature of the solute. This property can therefore be used to determine the molar mass of a solute. The difference between the freezing point of pure solvent T and that of the solution Tr is called the freezing point depression, ATr. The freezing point depression depends on the heat of fusion of the solid, AHrus, and the ratio of solute to solvent molecules in the solution. The latter is conveniently measured by the molality, which is defined as the number of moles of solute per kilogram of PURE SOLVENT. AT is therefore determined by: AT - Kexm where K. the freezing point depression constant into which AH, is incorporated), is a characteristic of the solvent, and m, the molality, is a measure of the concentration of the solute. If you know Kr and measure AT, then you can easily determine the molality of the solution. The solution is prepared by weighing a definite mass of solute and dissolving in a weighed mass of solvent. The m = moles solute kg solvent moles solute can be calculated by recognizing that the determined molality is: moles solute = (m)(kg solvent) When the moles of solute in the weighed mass of solute is known, it is easy to determine the molar mass (MM) of the solute: MM mass of solute moles solute When a pure solvent freezes, the temperature remains constant until all the liquid has solidified. When a solution freezes, it is the solvent that solidifies and the remaining solution will become increasingly more concentrated and the freezing temperature will therefore decrease accordingly.