Question

The relationship between osmotic pressure at 273 K when 10 g glucose, 10 g urea and 10 g sucrose are dissolved in 250 mL of water to form separate solutions is:
[$P_1,P_2$ and $P_3$ are osmotic pressure of glucose,urea and sucrose solution respectivitely]

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

Answer 1

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

None of the solutes are electrolytes.

$\pi =CRT=\frac{m\times R\times T}{M_w\times V}$

Since osmotic pressure is directly related to concentration, if the concentration increases, the pressure increases. Urea has the lowest molecular weight of $60g.mo{l}^{-1}$ and therefore, the concentration of urea would be the highest. Sucrose has the highest molecular weight of $342g.mo{l}^{-1}$ followed by glucose $180g.mo{l}^{-1}$. Following the same logic, we get the order of concentration: urea > glucose > sucrose.