Question

An electrolyte $A$ gives $3$ ions and $B$ is a non- electrolyte. If $0.1M$ solution of $B$ produces an osmotic pressure $P$, then $0.05M$ solution of $A$ will produce an osmotic pressure, assuming that the electrolyte is completely ionised:

• A. $1.5P$
• B. $P$
• C. $0.5P$
• D. $0.75P$

Answer 1

Answer: (A)

$1.5P$

The electrolyte '$A$ ' when completely ionised gives 3 ions, thus vant-off factor = $3$

'$B$ ' is a non -electrolyte, thus its vant-off factor = $1$

Osmotic pressure ($\pi$) = Concentration \times $R$ \times $T$

Osmotic pressure of '$B$ ' = $0.1RT$ $\times$ $i$ = $0.1RT$

$i=1$

Osmotic pressure of '$A$ ' = $0.05RT\times i$ = $0.05RT\times 3$ = $0.15RT$

$\therefore$ The osmotic pressure of electrolyte of $A$ is $1.5P$