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Calculate the vapour pressure lowering c...

Calculate the vapour pressure lowering caused by the addition of `68.4 g` of sucrose (molecular mass = 342) to `500 g` of water if the vapour pressure of pure water at `25^(@)C` is `20.0 mm Hg`.

Text Solution

Verified by Experts

According to Raoult's law
`(P^(@)-P_(S))/(P^(@)) = (n_(2))/ (n_(2)+n_(1)) = chi_(2)`
or `DeltaP = (n_(2))/(n_(2)+n_(1)) P^(@)`
Given, `n_(2) = (68.4)/(342) = 0.20`: `n_(1) = (500) /(18) = 27.78` and `P_(@) = 20.0`
substituing the values in the above equation, we get
`Delta P = (0.20)/(0.20 + 27.78) xx 20.0 = 0.142 mm Hg`
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Knowledge Check

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