Question

A solution was made by dissolving 5.10 mg of hemoglobin in water to give a final volume of 1.00 ml. the osmotic pressure of this solution was 1.95×10-3 atm at 25.0°c.

Answer 1

The molecular weight of hemoglobin can be calculated using osmotic pressure

Osmotic pressure is a colligative property and it depends on molarity as

πV = nRT

where

π = osmotic pressure

V = volume = 1mL = 0.001 L

n = moles

R = gas constant = 0.0821 L atm / mol K

T = temperature = 25°C = 25 + 273 K = 298 K

Putting values we will get value of moles

`moles=(\pi V)/(RT)=(0.00195X0.001)/(0.0821X298)mol`

we know that

`moles=(mass)/(molarmass)`

Therefore

`molarmass=(mass)/(moles)=(5.10X10^(-3)g)/(7.97X10^(-8))=6.399X10^(4)g`