Cliffs AP Chemistry, 3rd Edition

10. At 37°C and 1.00 atm of pressure, nitrogen dissolves in the blood at a solubility of

6.0× 10 –4 M. If a diver breathes compressed air where nitrogen gas constitutes 80. mole %

of the gas mixture, and the total pressure at this depth is 3.0 atm, what is the concentration

of nitrogen in her blood?

A. 1.4 × 10 –4M

B. 6.0 × 10 –4M

C. 1.0 × 10 –3M

D. 1.4 × 10 –3 M

E. 6.0 × 10 –3M

Answer: D

Determine k by using C= kP(Henry’s law).

..
k pressure N.
concentration N
atm

60 10 M 60 10 M atm

100

(^441)
2
===^2 # - #:--
To solve the problem
P = 0.80 ×3.0 atm = 2.4 atm
CkP ...
liter atm
60 10 moles 24 atm 14 10 M
1
#^43
== : ##=

11. The vapor pressure of an ideal solution is 450. mm Hg. If the vapor pressure of the pure
    solvent is 1000. mm Hg, what is the mole fraction of the nonvolatile solute?

A. 0.450

B. 0.500

C. 0.550

D. 0.950

E. None of the above

Answer: C

P 1 = X 1 P 1 °

P.

.
X P mm Hg.

mm Hg

1000

450

1 ==^1 =0 450

1 %

The mole fraction of the solute is

1.000 −Xl= 1.000 −0.450 = 0.550

Solutions