Arginine vasopressin is a pituitary harmone. It helps to regulate the amount of water in the blood by reducing the flow of urine from the kidneys. An aqueous solution containing `21.6 mg` of vasopressin in `100 mL` of solution contaning had an osmotic pressure of `3.70 mm Hg` at `25^(@)C`. What is the molecular weight of the harmone?

Explanation

Given vasopressin `= 21.6 mg = 21.6 xx 10^(-3) g`,
`V_("solution") = 100 mL = (100)/(1000) litre`,
`pi = 3.70 mm = (3.70)/(760) atm`,
`T = 25+273 = 298 K`
`because piV = (w)/(m)ST`
`:. (3.70)/(760) xx (100)/(1000) = (21.6 xx 10^(-3))/(m) xx 0.0821 xx 298`
`m = 1085 g mol^(-1)`