Question

Catalase (a liver enzyme) dissolves in water. A 14mL solution containing 0.166g of catalase exhibits an osmotic pressure of 1.2 Torr at 20°C. What is the molar mass of catalase?

Answer 1

Answer:

The correct answer is 180,424 g/mol

Explanation:

The expression for osmotic pressure (π) is the following:

π= i x M x R x T

Where M is the molarity of the solution, R is the gas constant and T is the temperature.

i= 1 because the catalase is a nonelectrolyte.

M= m/(VxMW) because the molarity is in mol/L and mol is obtained by the mass (m) divided into the molecular weight (MW)

We introduce this expression in the expression for osmotic pressure and we obtain:

π= $\frac{m R T }{V MW}$

T= 20ºc= 293 K

V= 14 mL= 0.014 L

So, we directly calculate the molecular weight as follows:

MW= $\frac{m R T}{V \pi }$

MW= (0.166 g)(0.082 LatmK⁻¹mol)(293 K) (760Torr atm⁻¹)/(0.014 L)(1.2 Torr)

MW= 180,424 g/mol

For an enzyme: 180,424 g/mol= 180.4 kDa (because 1 g/mol= 1 Da)