Solved Examples of Osmotic Pressure
Question 1: Calculate the osmotic pressure of 5% solution of cane sugar (sucrose) at the temperature of 15° Celsius.
Solution:
m = molecular mass of sucrose (C12H22O11) = 342 amu
w = 5g
V = 100 mL = 0.1 litre
we know, R = 0.0821 L⋅atm⋅K−1⋅mol−1,
T = (15 + 273) = 288 K
and as glucose is the non-ionic compound and doesn’t dissociate to give any ions in the solution, it’s van’t Hoff factor is 1.
Rearranging ∏ = iCRT, we get ∏V = w/m ⋅RT,
∏ = 5/342×1/0.1 × 0.082 × 288 = 3.453 atm
Question 2: The solution containing 10 g of an organic non-ionic compound per liter showed an osmotic pressure of 1.16 atmosphere at 0° Celsius. Calculate the molecular mass of the compound (S = 0.0821 L⋅atm⋅K−1⋅mol−1)
Solution:
As compound is non-ionic, it’s van’t Hoff factor is 1.
Applying the equation m = w/∏V ⋅RT
Given w = 10 g, P = 1.18 atm, V = 1 litre, S = 0.0821 L⋅atm⋅K−1⋅mol−1 and T = 273 K.
m = 10/1.18×1 × 0.0821 × 273 = 189.94 amu
Osmosis and Osmotic Pressure
A solution is a homogeneous mixture of two or more particles having particle sizes smaller than one nanometer. Sugar and salt solutions in water, as well as soda water, are common examples of solutions. In a solution, all of the components appear as a single phase. There is particle homogeneity, which means that the particles are evenly dispersed. This is why a full bottle of soft drink tastes the same.
The component that dissolves the other component is known as the solvent. Solute refers to the component(s) that are dissolved in the solvent (s). In general, the solvent is present in greater proportion than the solute. The solute amount is less than the solvent amount. Solutes and solvents can exist in every state of matter, including solids, liquids, and gases. A liquid solution is composed of a solid, liquid, or gas dissolved in a liquid solvent. Solid and gaseous solutions are represented by alloys and air, respectively.