`100 mL` of `1.0 g` sample of a drug having compound `C_(21)H_(23)O_(5)N` as drug is coated with sugar lactose (mol.wt.342) exerts the osmotic pressure of `0.70 atm` at `27^(@)C`. What is the drug percentage in sample?

Explanation

Let a, b g are the amount of drug `(Mw=369)` and sugar `(Mw=342)`, respectively
`a+b=1.0` …(i)
`:.piV=(n_(1)+n_(2))RT`
`0.70xx(100/1000)=[a/369+b/342]xx0.0821xx300`
`342a+369b=358.66` ..(ii)
By Eqs.(i) and Eqs.(ii)
`a=0.617 g`
`b=0.383 g`
`:.% of drug =0.617/1xx100=61.7%`