Question

A chemist is trying to determine the molar mass of a certain protein. 1.00 x 10 -3 g of it was dissolved in enough water to make 1.00 mL of solution. The osmotic pressure of this solution was found to be 1.12 torr at 25.0°C. Calculate the molar mass of the protein.

Answer 1

Molar mass of protein is
`1.66* 10^(4)` g/mol

Step-by-step explanation:

Protein is a non-electrolyte. For a non-electrolyte-

We know,
`\pi =c.R.T`

where
`\pi` represents osmotic pressure of solution, c represents molarity of solution and T represents temperature in kelvin scale.

Let's assume molar mass of protein is M g/mol

Then
`c=((1.00* 10^(-3))/(M))/(1.00)* 1000mol/L=(1.00)/(M)mol/L`

R = 0.0821 L.atm/(mol.K)

`\pi` = 1.12 torr = 0.00147 atm

T = (273+25) K = 298 K

So,
`0.00147=(1.00)/(M)* 0.0821* 298`

or, M =
`1.66* 10^(4)`

So, molar mass of protein is
`1.66* 10^(4)` g/mol