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Concentration Worksheet - Concentration Units


									                         Concentration Units
               Molarity (M) (mol solute)/(L of solution)
             % by mass (g solute/g of solution) x 100 %
               Molality (m) (mol solute)/kg of solvent)
             mole fraction (X) (mol solute)/(total moles)

1. Calculate the percentage by mass of the solute in a solution of 5.50g
   of NaBr in 78.2 g of solution

2. Calculate the amount of water that must be added to 5.00g of urea
   (NH2)2CO to make a 16.2 percent by mass solution

3. Calculate the molality of a solution that contains 14.3 g of sucrose
   (C12H22O11) in 676 g of water.

4. Calculate the molality of a 1.22 M sucrose solution. The density of the
   solution is 1.12 g/mL.

5. What is the mole fraction of sugar in a 1.22 M solution of sucrose?
6. The density of a solution containing 10.0 % ethanol (C2H5OH) by mass
   is 0.984 g/mL. What volume of this solution would contain 0.125 mol
   of ethanol?

                       Colligative Properties
         PA=PA°XA                 Tb=Kbm          =MRT
                  P=PA°XB                 Tf=Kfm

7. The vapor pressure of a glucose(C6H12O6) solution is 17.01 torr at
   20°C while that of pure water is 17.25 torr at the same T. What is
   the molality of the solution?

8. Ethylene glycol, CH2(OH)CH2(OH), is a common automolbile antifreeze.
   It is water soluble and faorly nonvolatile (b.p=197°). Calculate the
   freezing point of a solution containing 651 g of EG in 2505g of water.
   Would you keep this solution in your car in the summer? (Kb and Kf for
   water are 0.52°C/m and 1.86°C/m respectively.)
9. The average osmotic pressure of seawater is about 30.0 atm at 25°C.
   calculate the molar concentration of an aqueous solution of urea that
   is isotonic with seawater.

10. A 0.86 percent by mass solution of NaCl is called “physiological saline”
    because its osmotic pressure is equal to that of the solution in red
    blood cells. Calculate the osmotic pressure of this solution at normal
    body Temperature (37°C). The density of the saline solution is 1.005

11. A forensic chemist is given a white powder for analysis. She
   dissolves 0.50 g of the substance in 8.0 g of benzene (C6H6). The
   solution freezes at 3.9°C. Can she conclude that the substance is
   probably cocaine (C17H21NO4) ?(Pure benzene freezes at 5.5° C and Kf
   for benzene is 5.12°C/m).

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