InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
Freezing point of urea solution is `-0.6^(@)C`. How much urea (M.W. = 60 g/mole) is required to dissolve in 3 kg water `(K_(f) = 1.5^(@)Ckg mol^(-1))`A. 3.6 gB. 2.4 gC. 7.2 gD. 6.0 g |
|
Answer» Correct Answer - C `Delta T_(f)=K_(f)xx(1000xxW_(A))/(M_(A)xxW_(B))` [where `W_(A)` = weight of solute, `W_(B)` = weight of solvent, `M_(A)` = molecular weight of solute] or, `0-(-0.6)=(1.5xx1000xxW_(A))/(60xx3000)` or, `W_(A)=(60xx3000xx0.6)/(1.5xx1000)=72g` If we consider the mass of water given to 300 gram `0.6^(@)C=(1000g kg^(-1)xx1.5^(@)Ckg mol^(-1)xx " weight of urea")/(60g mol^(-1)xx300 g)` `therefore` Weight of urea = 7.2 g. |
|