The freezing point of 42.30 g of a pure solvent is measured to be 43.64 °C. When 2.84 g of an unknown solute (assume the van 't Hoff factor = 1.0000) is added to the solvent the freezing point is measured to be 40.86 °C. Answer the followingquestions (the freezing point depression constant of the pure solvent is 7.46 °C-kg solvent/mol solute).What is the molality of the solution?How many moles of solute are present?molWhat is the molecular weight of the solute?g/mol

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Answered: The freezing point of 42.30 g of a pure…

Chemistry: Principles and Practice

3rd Edition

ISBN:9780534420123

Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer

Publisher:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer

Chapter12: Solutions

Section: Chapter Questions

Problem 12.86QE

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Similar questions

A solution is made by dissolving 34.0 g of NaCl in 100 g of H2O at 0C. Based on the data in Table 8-1, should this solution be characterized as a. saturated or unsaturated b. dilute or concentrated
Carbon tetrachloride (CCl4) and benzene (C6H6) form ideal solutions. Consider an equimolar solution of CCl4 and C6H6 at 25C. The vapor above the solution is collected and condensed. Using the following data, determine the composition in mole fraction of the condensed vapor. Substance Gfo C6H6(l) 124.50 kJ/mol C6H6(g) 129.66 kJ/mol CCI4(l) 65.21 kJ/mol CCI4,(g) 60.59 kJ/mol
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 listed in Table 10-5, 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.
You make 20.0 g of a sucrose (C12H22O11) and NaCl mixture and dissolve it in 1.00 kg water. The freezing point of this solution is found to be 0.426C. Assuming ideal behavior, calculate the mass percent composition of the original mixture, and the mole fraction of sucrose in the original mixture.
A gaseous solute dissolves in water. The solution process has H=15 kJ. Its solubility at 22C and 6.00 atm is 0.0300 M. Would you expect the solubility to be greater or less at (a) 22C and 1 atm? (a) 18C and 6 atm? (a) 15C and 10 atm? (a) 35C and 3 atm?
Which solute has the greatest effect on the boiling pointof 1.00 kg of water: 50.0 g of strontium chloride (SrCl2) or 150.0 g of carbon tetrachloride (CCl4) ? Justify youranswer.
The vapor pressures of several solutions of water-propanol (CH3CH2CH2OH) were determined at various compositions, with the following data collected at 45C: H2O Vapor pressure(torr) 0 74.0 0.15 77.3 0.37 80.2 0.54 81.6 0.69 80.6 0.83 78.2 1.00 71.9 a. Are solutions of water and propanol ideal? Explain. b. Predict the sign of Hsoln for water-propanol solutions. c. Are the interactive forces between propanol and water molecules weaker than, stronger than, or equal to the interactive forces between the pure substances? Explain. d. Which of the solutions in the data would have the lowest normal boiling point?
A forensic chemist is given a white solid that is suspected of being pure cocaine (C17H21NO4, molar mass = 303.35 g/mol). She dissolves 1.22 0.01 g of the solid in 15.60 0.01 g benzene. The freezing point is lowered by 1.32 0.04C. a. What is the molar mass of the substance? Assuming that the percent uncertainty in the calculated molar mass is the same as the percent uncertainty in the temperature change, calculate the uncertainty in the molar mass. b. Could the chemist unequivocally state that the substance is cocaine? For example, is the uncertainty small enough to distinguish cocaine from codeine (C18H21NO3, molar mass = 299.36 g/mol)? c. Assuming that the absolute uncertainties in the measurements of temperature and mass remain unchanged, how could the chemist improve the precision of her results?
Distinguish between a strong electrolyte, a weak electrolyte, and a nonelectrolyte. How can colligative properties be used to distinguish between them? What is the vant Hoff factor? Why is the observed freezing-point depression for electrolyte solutions sometimes less than the calculated value? Is the discrepancy greater for concentrated or dilute solutions?
An aqueous solution containing 0.250 mole of Q, a strong electrolyte, in 5.00 102 g water freezes at 2.79C. What is the vant Hoff factor for Q? The molal freezing-point depression constant for water is 1.86C kg/mol. What is the formula of Q if it is 38.68% chlorine by mass and there are twice as many anions as cations in one formula unit of Q?
The dispersed phase of a certain colloidal dispersion consists of spheres of diameter 1.0 102 nm. (a) What are the volume (V=43r2) and surface area (A = r2) of each sphere? (b) How many spheres are required to give a total volume of 1.0 cm3? What is the total surface area of these spheres in square meters?

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