Assume that a portable reverse-osmosis apparatus operates on seawater, whose concentrations of constituent ions are listed in Table, and that the desalinated water output has an effective molarity of about 0.02 M. What minimum pressure must be applied by hand pumping at 297 K to cause reverse osmosis to occur?
Table: Ionic constituents of Seawater Present in Concentrations Greater Than 0.001 g/kg(1 ppm)
| Ionic Constituent |
Salinity |
Concentration (M) |
Chloride, Cl-
|
19.35 |
55 |
| Sodium, Na+ |
10.76 |
0.47 |
| Sulfate, SO42- |
2.71 |
0.028 |
| Magnesium, Mg2+ |
1.29 |
0.054 |
| Calcium, Ca2+ |
0.412 |
0.01 |
Potassium, K+
|
0.4 |
1110 |
Carbon dioxide*
|
0.106 |
2.3 X 10-3 |
Bromide, Br-
|
0.067 |
83 X 10-4 |
| Boric acid, H3B03 |
0.027 |
4.3 X 10-4 |
Strontium, Sr2+
|
0.0079 |
9.1 X 10-5 |
| Fluoride, F- |
0.0013 |
7.0 X 10-5 |