Question

'w' g of a non-electrolytic compound (molar mass $=200)$ are dissolved in one litre of 0.05 M NaCl aqueous solution. The osmotic pressure of this solution is found to be 4.92 atm at ${27}^{o}C$. The value of 'w/10' in gm is:
( Assume complete dissociation of NaCl and ideal behaviour of this solution)

Write the answer in the nearest integer.

Answer 1

Given that, $\pi =4.92atm,T=27+273=300K,V=1litre$

$n_1=$ mole of non-electrolyte $=w/200$

$n_2=$ mole of NaCl $=0.05$

Using $\pi V=nST$ for a solution containing non-electrolyte and $NaCl$,

$\pi V=n_{1}ST+n_2(1+\alpha )ST$

$\pi V=[n_1+n_2(1+\alpha \left)\right]ST$

where, $\alpha =1$ given for NaCl

$\therefore 4.82\times 1=[\frac{w}{200}+0.05\times 2]\times 0.082\times 300$

$\therefore w=20g$

$\therefore \frac{w}{10}=\frac{20}{10}=2$