# Calculate the amount of CaCl2 (van't Hoff factor i = 2·47) dissolved in 2·5 L solution so that its osmotic pressure at 300K is 0·75 atmosphere. - Chemistry

Numerical

Calculate the amount of CaCl2 (van't Hoff factor i = 2.47) dissolved in 2.5 L solution so that its osmotic pressure at 300K is 0.75 atmosphere.

Given : Molar mass of CaCl2 is 111g mol-1

R=0.082 L.atm K-1mol-1

#### Solution

Data : V = 2.5 L

T = 300 K

pi=0.75atm

Molar mass of CaCl2 = M2 = 111g/mol

R = 0.082 L.atm.k-1mol-1.

Solution :

i=(pi_(obs))/(pi_(cal)

2.47=0.75/pi_(cal)

pi_(cal)=0.75/2.47

pi_(cal)=0.303atm

piV=nRT

:.piV=W_2/M_2xxRxxT

:.pi_(cal)xxV=W_2/M_2xxRxxT

:.W_2=(pi_(cal) xxVxxM_2)/(RxxT)

=(0.303xx2.5xx111)/(0.082xx300)

 W2=3.417gm

Mass of CaCl2=3.417gm

Concept: Colligative Properties and Determination of Molar Mass - Introduction
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