Transcript More on Solutions

More on Solutions
PGCC CHM 101 Sinex
Aqueous Solubility
Fatty Acids: R-COOH
where R is 12-22 carbons
How does the chain length influence solubility?
Why the difference in water and benzene?
What happens to the freezing point of water
as a solute is added?
0.0
0.0
0.0
water
FPFP
water
FP
water
0
0
0
-1
-1
-2
-2
-2
-4
-3
-3
-4
-6
-4
-5
-5
-8
-6
-6
-10
-7
-7
-8
-12
-8
Freezing
Point
Depression
Freezing
Depression
Freezing
Point
Depression
0.5
1.0
1.5
0.5
0.5
1.0
1.0
1.5
1.5
2.0
2.0
2.0
i=1
sugar
i=2
sugar
NaCl
sugar
NaCl
Na2SO4
molar
molar
concentration
molar concentration
concentration
What happens if the solute is an electrolyte?
The number of particles controls the change!
i=3
Colligative Properties
pressure
As the concentration of solute increases:
1
fp
bp
boiling point - elevated
freezing point - depressed
vapor pressure - lowered
temperature
water (solvent)
aqueous solution
Red Blood Cells
Let’s examine the influence of environment on the RBC
cell membrane
0.1 M NaCl
water diffuses into cell
0.5 M NaCl
1.0 M NaCl
water diffuse out of cell
What is happening in the various NaCl solutions?
osmotic pressure simulation
Osmosis and Osmotic Pressure
semi-permeable membrane
C2 > C1
Dheight
C2 = C1
C1
C1 increases
due to loss
of water
C2
Dheight is
dependent on
concentration
difference = p,
the osmotic
pressure
C2 decreases
due to dilution
by water
only water, the solvent, migrates through membrane
diffusion due to concentration gradient
osmotic pressure, p
How is osmotic pressure influenced by
concentration and temperature?
p = kC
y = mx + b
450K
298K
p = ik’C
p = iTk’’C
p = iRTC
concentration, M
where iRT
is the slope
and R is the
gas constant
Reverse osmosis for desalination
Now let’s
apply a pressure
where P = pseawater
pseawater = iRTC
where C = 0.5 M
NaCl
fresh water
seawater
Which way does water migrate?
more fresh water is produced
Now let’s
apply a
pressure
where
P > pseawater
no migration
seawater becomes saltier