MHT CET202014 Oct 2020Evening ShiftChemistrySolutionsActual
What is the value of K _ f if 30 ~g urea (molar mass 60 ) dissolved in 0.5 dm ³ of water decreases freezing point by 0 15^ C ?
Options
- A0 15 ~K ~kg ~mol ⁻¹
- B0.030 Kkg mol ⁻¹
- C0.30 Kkg mol ⁻¹
- D0.015 Kkg mol ⁻¹
Correct answer
A. 0 15 ~K ~kg ~mol ⁻¹
Step-by-step solution
Mass of water =0.5 dm ³=0.5 ~kg Moles of urea = 30 60 =0.5 mole Molality of urea = 0.5 ~mol 0.5 ~kg =1 ~mol / kg T _ f = K _ f m K _ f = T _ f m = 0.15 ~K 1 ~mol / kg =0.15 Kmol ⁻¹ ~kg