lab 3 postlab

lab 3 postlab - questions below and identify the unknown...

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Freezing point depression can be used to experimentally determine the van't Hoff factor of a solute in solution. Given the data in the table, please answer the questions below and determine the "real" van't Hoff factor of the solute. Expermimental Results Mass of solvent (water) 5.266 g Freezing point of water 0.00 °C Freezing point depression constant (K f ) of water 1.86 °C/m Mass of solution 6.016 g Freezing point of solution -3.28 °C a. What mass of solute was used? .750 g b. What is the freezing point depression, T f , of the solution? 3.28 °C c. What is the colligative molality, m c , of the soltion? 1.76 m d. How many moles of solute particles are present in solution? .00927 moles e. If the solute has a molar mass of 318.21, what is the van't Hoff factor, i, for the solute? (Remember that experimentally, i does not have to be an integer!) i = 3.94 Another way that freezing point depression can be useful is to experimentally determine the molar mass of an unknown solute in solution. Please use the data in the table to answer the
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Unformatted text preview: questions below and identify the unknown solute. Expermimental Results Mass of solvent 10.117 g Freezing point of pure solvent 24.8 °C Freezing point depression constant (K f ) of the solvent 8.95 °C/m Mass of solution 10.924 g Freezing point of solution 18.9 °C a. What mass of solute was used? .807 g b. What is the freezing point depression, T f , of the solution? 5.9 °C c. What is the colligative molality, m c , of the soltion? .66 m d. Assuming a van't Hoff factor (i) of 1, how many moles of solute are present in solution? .0067 moles e. What is the molar mass of the solute? 120 g/mol f. From the list below, what is the unknown? Unknown Molar Mass Crisco Vegetable Oil 605 g/mol Havoline Motor Oil 511 g/mol Rosonol Lighter Fluid 121 g/mol Crisco Vegetable Oil Havoline Motor Oil Rosonol Lighter Fluid...
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This note was uploaded on 03/18/2011 for the course CHEM 202 taught by Professor Feducia during the Spring '09 term at N.C. State.

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lab 3 postlab - questions below and identify the unknown...

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