Question

Seawater contains 32.8 g of salts for every liter of solution. Assuming that the solute consists entirely of NaCl (in fact, over 90% of the salt is indeed NaCl), calculate the osmotic pressure of seawater at 20 âC . Express the osmotic pressure in atmospheres to three significant figures.

Answer 1

Osmotic pressure is π = 27.6 atm

Step-by-step explanation:

32.8 g of salts for every liter of solution can we understood as Molarity, but have to convert, the mass to moles (mass / molar mass)

32.8 g NaCl / 58.45 g/m = 0.561 moles

These are the moles of solute in 1L of solution.

Let's calculate the osmotic pressure by the formula

π = M . R . T . i

M, means molarity

R means Universal gases constant → 0.082 L.atm/ mol.K

T means absolute temperature (K) → 20°C + 273 = 293K

i = Van't Hoff factor, for NaCl i = 2

NaCl → Na⁺ + Cl⁻

π = 0.561 mol/L . 0.082 L.atm/ mol.K . 293K .2

π = 27.6 atm