Q.

What weight of glucose must be dissolved in 100 g of water to lower the vapour pressure by 0.20 mm Hg

(Assume dilute solution is being formed)

Given: Vapour pressure of pure water is 54.2 mm Hg at room temperature. Molar mass of glucose is 180 g mol-1.                [2023]

1 3.69 g  
2 2.59 g  
3 3.59 g  
4 4.69 g  

Ans.

(1)

For a solution PA0-PsPs=nN (for dilute solution)

                             54.2-5454=w/180100/18

Amount of glucose(w)=20054=3.69 g