Question

Arrange the following solutions in the increasing order of their osmotic pressure
(i) $34.2g/L$ sucrose $(M=342)$
(ii) $60g/L$ urea $(M=60)$
(ii) $90g/L$ glucose $(M=180)$
(vi) $58.5g/LNaCl(M=58.5)$

• A. Sucrose < Urea < Glucose < NaCl
• B. Sucrose < Glucose < NaCl < Urea
• C. Sucrose < Glucose < Urea < NaCl
• D. NaCl < Urea < Glucose < Sucrose

Answer 1

Answer: (C)

Osmotic pressure is a colligative property, the property of the solution which depends only on the number of solute particles.
$(i)34.2g/L$ sucrose $=0.1$ mole sucrose in $1L$ solution
$(ii)60g/L$ urea $=1$ mole urea in $1L$ solution.
$(iii)90g/L$ glucose $=0.5$ mole glucose in $1L$ solution.
$(vi)58.5g/LNaCl=1molNaCl$ in $1L$ solution
Sucrose, urea and glucose do not dissociate into their ions while $1$ mole $NaCl$ gives $2$ mole particles i.e., $N{a}^{+}$ and $C{l}^{-}$ ions.
Hence, the correct increasing order of their osmotic pressure is sucrose < glucose < urea < $NaCl$. Solutions.