Assuming that the solute consists entirely of nacl (over 90% is), calculate the osmotic pressure of seawater at 20∘c.

The osmotic pressure of seawater at 20∘c. = 3.12 atm

Osmotic pressure is the minimum pressure applied to the solution so that there is no osmotic transfer from a thinner solution to a more concentrated solution.

General formula:

π = osmosis pressure (atm)

M = concentration of solution (mol / l)

R = constant = 0.08205 L atm mol-1 K-1

T = Temperature (Kelvin)

The full question should be:

Seawater contains 3.8g of salts for every liter of solution.

Assuming that the solute consists entirely of NaCl (over 90% is), calculates the osmotic pressure of seawater at 20 degrees Celsius.

mole NaCl = 3.8 gram: 58.5 (molar mass of NaCl)

mole NaCl = 0.065

so the molarity = 0.065 M

For NaCl electrolyte solutions, the van't Hoff factor (i) is taken into account. And the value of i for strong electrolytes such as NaCl which has a degree of ionization = 1 then i = n = 2 (NaCl ionizes into 2 ions namely Na + and Cl-)

Temperature = 20° C+ 273 = 293 K

then

π = M. R. T. i

π = 0.065. 0.082. 293. 2

π = 3.12 atm

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Keywords: osmotic pressure, electrolyte solution