a) In reverse osmosis, water flows out of a salt solution until the osmotic pres
ID: 913807 • Letter: A
Question
a) In reverse osmosis, water flows out of a salt solution until the osmotic pressure of the solution equals the applied pressure. If a pressure of 65.0 bar is applied to seawater, what will be the final concentration of the seawater at 20 °C when reverse osmosis stops?
?=Mc
b) Assuming that seawater has a total ion concentration (a.k.a colligative molarity) of 1.10 Mc, calculate how many liters of seawater are needed to produce 38.1 L of fresh water 20 degrees C with an applied pressure of 65.0 bar.
?=L
Explanation / Answer
a) = McRT
= 65 bar
R = 0.083145 L bar / mol K
T = 20 + 273 = 293 K
Mc = ?
Mc = / RT
Mc = 65 / (0.083145 x 293) = 2.66 Mc
b) C1V1 = C2V2 or M1V1 = M2V2
(1.10 Mc) (x + (1.1 Mc x 38.1 L)) = 2.66 Mc
(1.10 Mc) (x + 41.91) = 2.66 Mc
41.91 = 2.66 – 1.10 (x)
x = 41.91 / (2.66 – 1.10)
x = 26.86
V1 = 26.86+ 41.91 = 68.77L salt water
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