(3) A 300.0 mg sample of caffeine was dissolved in 10.0 g of camphor (K+= 39.7°C/kgmol.) The freezing point of camphor decreases by 3.07 °C. What isthe calculated molar mass of caffeine? Show your work. (4) Compare the calculated molar mass of caffeine with the known molar massof caffeine. Based on this information, what should be van't Hoff factor befor caffeine? Explain.

(3). To calculate the molar mass of caffeine, we can use the freezing point depression…

Answered: (3) A 300.0 mg sample of caffeine was…

Chemistry: The Molecular Science

5th Edition

ISBN:9781285199047

Author:John W. Moore, Conrad L. Stanitski

Publisher:John W. Moore, Conrad L. Stanitski

Chapter13: The Chemistry Of Solutes And Solutions

Section: Chapter Questions

Problem 77QRT

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Similar questions

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.
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
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?
6-67 Calculate the freezing points of solutions made by dissolving 1.00 mole of each of the following ionic solutes in 1000. g of H2O. (a) NaCI (b) MgCI2 (c) (NH4)2CO3 (d) AI(HCO3)3
6-111 As noted in Section 6-8C, the amount of external pressure that must be applied to a more concentrated solution to stop the passage of solvent molecules across a semipermeable membrane is known as the osmotic pressure The osmotic pressure obeys a law similar in form to the ideal gas law (discussed in Section 5-4), where Substituting for pressure and solving for osmotic pressures gives the following equation: RT MRT, where M is the concentration or molarity of the solution. (a) Determine the osmotic pressure at 25°C of a 0.0020 M sucrose (C12H22O11) solution. (b) Seawater contains 3.4 g of salts for every liter of solution. Assuming the solute consists entirely of NaCl (and complete dissociation of the NaCI salt), calculate the osmotic pressure of seawater at 25°C. (c) The average osmotic pressure of blood is 7.7 atm at 25°C. What concentration of glucose (C6H12O6) will be isotonic with blood? (d) Lysozyme is an enzyme that breaks bacterial cell walls. A solution containing 0.150 g of this enzyme in 210. mL of solution has an osmotic pressure of 0.953 torr at 25°C. What is the molar mass of lysozyme? (e) The osmotic pressure of an aqueous solution of a certain protein was measured in order to determine the protein's molar mass. The solution contained 3.50 mg of protein dissolved in sufficient water to form 5.00 mL of solution. The osmotic pressure of the solution at 25°C was found to be 1.54 torr. Calculate the molar mass of the protein.
The Rast method uses camphor (C10H16O) as a solvent for determining the molar mass of a compound. When 2.50 g of cortisone acetate are dissolved in 50.00 g of camphor (k f =40.0C/m), the freezing point of the mixture is 173.44C; that of pure camphor is 178.40C. What is the molar mass of cortisone acetate?
6-53 Dioxin is considered to be poisonous in concentrations above 2 ppb. If a lake containing L has been contaminated by 0.1 g of dioxin, did the concentration reach a dangerous level?
6-74 An osmotic semipermeable membrane that allows only water to pass separates two compartments, A and B. Compartment A contains 0.9% NaCI, and compartment B contains 3% glycerol C3H8O3. (a) In which compartment will the level of solution rise? (b) Which compartment (if either) has the higher osmotic pressure?
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?
6-38 Describe how we would prepare 250 mL of 0.10 M NaOH from solid NaOH and water.
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?
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?

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