Question

Which one of the following solutions of compounds show highest osmotic pressure? $\left(A B, A B_{2}\right.$ and $A_{2} B_{3}$ are ionic compounds)

• A. $5.0\, M$ urea $i=1.0$ and temperature is $67^{\circ} C$
• B. $1.5\, M A _{2} B _{3}$ type $i=4.1$ and ternperature is $27^{\circ} C$
• C. $3.0\, M\, AB$ type $i=1.6$ and temperature is $27^{\circ} C$
• D. $2.5\, M\, A B_{2}$ type $i=2.5$ and temperature is $57^{\circ} C$

Answer 1

Answer: (D)

$\because \pi=$ ic $R T$, Thus

(a) $\pi$ for $5.0\, M$ urea is

$\pi=1 \times 5 \times R \times 340(T=67+273)$

$\pi=1700\, R$

(b) $\pi$ for $1.5\, M A_{2} B_{3}$ typè is $(i=4)$

$\pi=4.1 \times 1.5 \times R \times 300(T=27+273)$

$\pi=1800\, R .(\approx 1845)$

(c) $\pi$ for $3.0\, M\, A B$ type is $(i=1.6)$

$\pi=1.6 \times 3 \times R \times 300(T=27+273)$

$\pi=1440\, R$

(d) $\pi$ for $2.5\, M\, A B_{2}$ type is $(i=2.5)$

$\pi=2.5 \times 2.5 \times R \times 330(T=57+273)$

$\pi=2062.5\, R$