Question

The following solutions were prepared by dissolving $10g$ of glucose $\left(C_6{H}_{12}{O}_6\right)$ in $250ml$ of water $\left(P_1\right)$, $10g$ of urea $\left(C{H}_4{N}_{2}O\right)$ in $250ml$ of water $\left(P_2\right)$ and $10g$ of sucrose $\left(C_{12}{H}_{22}{O}_{11}\right)$ in $250ml$ of water $\left(P_3\right)$.
The right option for the decreasing order of osmotic pressure of these solutions is :

• A. $P_3>P_1>P_2$
• B. $P_2>P_1>P_3$
• C. $P_1>P_2>P_3$
• D. $P_2>P_3>P_1$

Answer 1

The correct option is B $P_2>P_1>P_3$

• Osmotic pressure $\left(\pi \right)=iCRT$
  where $C$ is molar concentration of the solution
• With increase in molar concentration of solution
  osmotic pressure increases.
• Since, weight of all solutes and its solution
  volume are equal, so higher will be the molar
  mass of solute, smaller will be molar
  concentration and smaller will be the osmotic
  pressure.
• Order of molar mass of solute decreases as
  Sucrose > Glucose > Urea
• So, correct order of osmotic pressure of solution
  is $P_3<P_1<P_2$