Solid iodine has a vapor pressure of 1.0 mmHg at 39 degree C. How many moles of

Question

Solid iodine has a vapor pressure of 1.0 mmHg at 39 degree C. How many moles of iodine will sublime into a 500 mL flask at this temperature? The vapor pressure of ethanol is 400 mmHg at 63.5 degree C. Its molar heat of vaporization is 39.3 kJ/mol. What is the vapor pressure of ethanol, in mmHg, at 34.9 degree C? Iridium has a radius of 136 pm and crystallizes in a face-centered cubic unit cell. What is the edge length of the unit cell? An element forms a body-centered cubic crystalline substance. The edge length of the unit cell is 287 pm and the density of the crystal is 7.92 g/cm^3. Calculate the atomic weight of the substance. (Avogadro's # = 6.022 times 10^23) Sodium hydroxide is available commercially as a 40.0% by weight aqueous solution. Calculate the molality of this sodium hydroxide solution. At 80 C, pure liquid A has a vapor pressure of 100 mm Hg and pure liquid B has a vapor pressure of 940 mm Hg. What is X_A for a solution of A and B with a normal boiling point of 80 C? Calculate the freezing point of a solution of 20.0 g methyl salicylate, C_7H_6O_2, dissolved in 800. g of benzene, C_6H_6. K_f is 5.10 C/m and the freezing point is 5.50 C for benzene. What is the molar mass of sucrose (table sugar) if a solution prepared by dissolving 0.822 g of sucrose in 300.0 mL of water has an osmotic pressure (pi) of 149 mm Hg at 298 K? [pi = MRT(R, gas constant = 0.08206 L.atm/K.mol)]

Explanation / Answer

24 )

NaOH weight % = 40 %

mass of NaOH = 40 g

molar mass of NaOH = 40 g / mol

moles of NaOH = mass / molar mass= 40 / 40 = 1

mass of solvent water = 60 g = 60 x 10^-3 kg = 0.06 kg

molality = moles / mass of solvent

              = 1 / 0.06

             = 16.7 m

molality of NaOH = 16.7 m

26)

solute methlsaicylate moles = 20 / 150.14 = 0.1332

mass of solvent = 800 g = 0.8 kg

molality = moles / mass of solvent

             = 0.1332 / 0.8

            = 0.1665 m

delta Tf = Kf x molality

detal Tf = 5.10 x 0.1665 = 0.849 oC

5.50 - Tf = 0.849

Tf = 4.65 oC

freezing point of solution = 4.65 oC

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