Assuming that sea water is a 3.5 wt % solution of NaCl in water,calculate its osmotic pressure at 20°C.The density of a 3.5% NaCl solution at 20°C is 1.023 g/mL.
A)1.0 atm
B)15 atm
C)29 atm
D)100 atm

Question

Quizplus · Accepted Answer

First, we need to calculate the molarity of the NaCl solution using the weight percent concentration:
3.5 g NaCl / 100 g solution x 1 mol NaCl / 58.44 g NaCl = 0.060 mol NaCl/L
Next, we can use the van't Hoff equation to calculate the osmotic pressure:
π = iMRT
π = (1) (0.060 mol/L) (0.08206 L atm mol^-1 K^-1) (293 K)
π = 1.75 atm
However, we need to convert from atm to bar:
π = 1.75 atm x 1.01325 bar/atm = 1.77 bar
Finally, we need to convert from bar to atm, since that is the unit given in the answer choices:
π = 1.77 bar / 1.01325 atm/bar = 1.75 atm, which rounds to Choice C, 29 atm.

Assuming That Sea Water Is a 3