(Solved): 2. The elemental analysis of an organic solid extracted from gum arabic (a gummy substance used in a ...

2. The elemental analysis of an organic solid extracted from gum arabic (a gummy substance used in adhesives, inks, and pharmaceuticals) showed that it contained 40.0 percent by mass C, 6.7 percent by mass H, and 53.3 percent by mass O. A solution of 0.691 g of the solid in 30.1 g of the solvent diphenyl gave a freezing-point depression of 1.53°C. Calculate the molar mass and molecular formula of the solid. (Kf for diphenyl is 8.00°C/m.)

molar mass:

___ × 10 ___ g/mol

(Enter your answer in scientific notation.)

3. Hemoglobin, the oxygen-transport protein, binds about 1.35 mL of oxygen per gram of the protein. The concentration of hemoglobin in normal blood is 150 g/L blood. Hemoglobin is about 95 percent saturated with O₂ in the lungs and only 74 percent saturated with O₂ in the capillaries. Calculate the volume of O₂ released by hemoglobin when 165 mL of blood flows from the lungs to the capillaries.

4. Calculate the molalities of the following aqueous solutions:

(a) 0.936 M sugar (C12H22O11) solution (density of solution = 1.095 g/mL)

___ m

(b) 1.21 M NaOH solution (density of solution 1.082 g/mL)

___ m

(c) 2.92 M NaHCO3 solution (density of solution 1.077 g/mL)

___ m

5. Calculate the pressure of O2 necessary to generate an aqueous solution that is 6.3 × 10?2 M in O2 at 25°C. The Henry's law constant for O2 in water at 25°C is 1.3 × 10?3 mol/L · atm.

___ atm

6. Determine the molality of an aqueous solution that is 19.5 percent urea by mass.

___m

7. A 254?mL sample of a sugar solution containing 1.13 g of the sugar has an osmotic pressure of
30.1 mmHg at 34.3°C. What is the molar mass of the sugar?

___ g/mol

8. Calculate the vapor pressure of a solution made by dissolving 235 g of urea
[(NH2)2CO; molar mass 60.06 g/mol] in 455 g of water at 25°C.

___ mm Hg (At 25°C, PH2O = 23.8 mmHg)

9. Be sure to answer all parts.

What are the boiling point and freezing point of a 3.15 m solution of naphthalene in benzene? (The boiling point and freezing point of benzene are 80.1°C and 5.5°C, respectively.)

Boiling point:

___°C

Freezing point:

___°C

10. How many liters of the antifreeze ethylene glycol [CH2(OH)CH2(OH)] would you add to a car radiator containing 6.75 L of water if the coldest winter temperature in your area is ?20.5°C? Calculate the boiling point of this water-ethylene glycol mixture. (The density of ethylene glycol is 1.11 g/mL.)

What is the volume of antifreeze?

___ L

What is the boiling point of the solution?

___°C