The nonvolatile, nonelectrolyte cholesterol , C27H46O (386.6 g/mol), is soluble in chloroform, CHCl3. How many grams of cholesterol are needed to generate an osmotic pressure of 2.61 atm when dissolved in 257 ml of a chloroform sol

10,6g of cholesterol are needed.

Explanation:

The formula of osmotic pressure is:

π = i×M×R×T

Where:

π is osmotic pressure (2,61atm), M is molarity of solution i is Van't Hoff's factor (1  for nonelectrolytes), R is gas constant (0,082atmL/molK), and T is temperature in Kelvin.

Assuming the temperature in the problem is 298K:

2,61 atm = 1×M×0,082atmL/molK×298K

0,107mol/L = M

In a solution of 257mL (0,257L), moles are:

0,257L×(0,107mol/L) = 0,027 moles. Using molecular mass:

0,027moles of cholesterol× (386,6g / mol) = 10,6g of cholesterol are needed.

I hope it helps!