Question

Assuming salts to be $90 \%$ dissociated, which of the following will have highest osmotic pressure?

• A. Decimolar $Al _{2}\left( SO _{4}\right)_{3}$
• B. Decimolar $BaCl _{2}$
• C. Decimolar $Na _{2} SO _{4}$
• D. A solution obtained by mixing equal volumes of (2) &(3) and filtering

Answer 1

Answer: (A)

$\pi= i ( CRT )$
For same $C$, and $T=(\pi \propto i)$
(1) $Al _{2}\left( SO _{4}\right)_{3} \longrightarrow \underset{i = 5}{2 Al ^{3+}}+3\left( SO _{4}^{2-}\right)$
(2) $BaCl _{2} \longrightarrow \underset{i = 3}{Ba ^{2+}}+2 Cl ^{-}$
(3) $Na _{2} SO _{4} \longrightarrow \underset{i = 3}{2 Na^{+}}+ SO _{4}^{2-}$
(1) have maximum (i) so its $\pi$ highest