# Molar mass problem

## Homework Statement

A 2.02-g sample of an enzyme is used to make a 6.00-mL solution. What is the molar mass of the enzyme if the osmotic pressure of the solution at 298K is 0.123 atm? Note that enzymes are nonelectrolytes

## Homework Equations

pi=MRT , R=.0821 L*atm*K^1-*mol^1-

## The Attempt at a Solution

pi=MRT => pi/RT=M=.123 atm/(298K)(.0821)=.00503 M

to find molar mass, I'd want to convert my concentration into grams/mol

.00503 M =.00503 mmol/1 mL
multiply (.00503 mmol/1mL)*(6.00 mL)= .0302 mmol => .00003016 mol enzyme

so molar mass = 2.02 g enzyme /.00003016 mol enzyme = 66976. 12732 g/mol , which is unusually enormous for a typical molar mass

I did the problem a few times and got the same answer. Althought it does seem high so I redid it a few times and kept getting the same answer. Maybe i'm missing something.

learningphysics
Homework Helper
The answer looks right to me.

chemisttree
Homework Helper
Gold Member
...so molar mass = 2.02 g enzyme /.00003016 mol enzyme = 66976. 12732 g/mol , which is unusually enormous for a typical molar mass

I assume that your answer is approximately 67,000 g/mol? This is 67 kilodaltons (kDa) which is well within the usual range for an enzyme.

i get the same, and expect big fat numbers for enzymes (as chemisttree points out)

4 to 1 :)