A protein subunit from an enzyme is part of a research study and needs to be characterized. A total of 0.180 g of this subunit was dissolved in enough water to produce 2.00 mL of solution. At 28C the osmotic pressure produced by the solution was 0.138 atm. What is the molar mass of the protein?

Question

A protein subunit from an enzyme is part of a research study and needs to be characterized. A total of 0.180 g of this subunit was dissolved in enough water to produce 2.00 mL   of solution. At 28C the osmotic pressure produced by the solution was 0.138 atm. What is the molar mass of the protein?

This is what i used:

PV= nRT
PV= (m/M)RT
Molar mass= (0.180g)(0.0821)(30lk)/(0.000276kg)(0.138)
= 16115.942

Which is wrong can someone please help me.

Saira · Accepted Answer

oops sorry when i multiply (0.002 Litres)(0.138) the answer i get is 0.000276 and kg was an accident

bobpursley · Answer

Where did you get .000276 kg. Shouldnt you have volume there..... 0.002liters?

DrBob222 · Answer

You have used the 0.138 twice. Once to multiply by 0.002 and again by sticking it in the denominator.Replace the 0.000276 with 0.002 L (that's the volume) and leave the 0.138 atm as is. I get something like 16,000 but you need to do it exactly.