A 15.0 mg sample of a protein was dissolved in water to produce 5.00 mL of solution at 25.1 $\circ$ C. The osmotic pressure of this solution was measured and found to be 6.50 torr. What is the molar mass of this protein?
A)427 g/mol
B)941 g/mol
C)8,580 g/mol
D)4,270 g/mol
E)561 g/mol

Question

Quizplus · Accepted Answer

Using the equation π = MRT, where π is the osmotic pressure, M is the molarity, R is the ideal gas constant, and T is the temperature in Kelvin, we can solve for the molarity of the protein solution:
π = MRT
6.50 torr = M(0.0821 L·atm/mol·K)(298 K)
M = 0.000333 M
Next, we can use the definition of molarity (M = moles solute / liters solution) to solve for the moles of protein in the solution:
0.000333 M = moles protein / 0.00500 L
moles protein = 0.00000167 mol
Finally, we can use the formula for molar mass (molar mass = mass / moles) to calculate the molar mass of the protein:
molar mass = 0.0150 g / 0.00000167 mol = 8,580 g/mol. Therefore, the correct answer is C.

A 150 Mg Sample of a Protein Was Dissolved in Water