Determine the amount of CaCl2 (i = 2.47) dissolved in 2.5 litre of water such that its osmotic pressure is 0.75 atm at 27°C.

Determine the amount of CaCl2 (i = 2.47) dissolved in 2.5 litre of water such that its osmotic pressure is 0.75 atm at 27°C.

Solution

Given that

Osmotic pressure π = 0.75 atm

Volume V = 2.5 liter

van’t Hoff factor i =  2.47

T = 27 +  273  = 300 K

Let w is the amount of CaCl₂ required

Gas constant R = 0.0821 L atm K^-1mol^-1

Molar mass of CaCl₂M = 1 × 40 + 2 × 35.5 = 111g mol^-1

Use the formula of osmotic pressure

 

Plug the values in this formula we get

W  = 3.43 g

Answer

Required amount of CaCl2 = 3.42 g.