Question

Insulin `(C_(2)H_(10)O_(5))_(n)` is dissolved in a suitable solvent and the osmotic pressure `(pi)` of solutions of various concentrations `(g//cm^(3))C` is measured at `20^(@)C`. The slope of a plot of `pi` against `C` is found to be `4.65 xx 10^(-3)`. The molecular weight of insulin is:
A. `4.8 xx 10^(5)`
B. `9 xx 10^(5)`
C. `3 xx 10^(5)`
D. `5.17 xx 10^(6)`

Answer 1

Correct Answer - D
`pi V = (w_(B))/(m_(B)) xx RT`
`pi = ((w_(B))/(V)) (RT)/(m_(B))`
`pi = C xx (RT)/(m_(B)) xx 1000` ....(i)
Where C = concentration in g/cc,
`y = x xx m`...(ii)
Comparing eqs. (i) and (ii) Slope `= (RT)/(m_(B)) xx 1000`
`m_(B) = (RT)/("Slope") xx 1000`
`= (0.0821 xx 293 xx 1000)/(4.65 xx 10^(-3))`
`= 5.17 xx 10^(6)`