Advertisements
Advertisements
प्रश्न
A 4% solution(w/w) of sucrose (M = 342 g mol–1) in water has a freezing point of 271.15 K. Calculate the freezing point of 5% glucose (M = 180 g mol–1) in water.
(Given: Freezing point of pure water = 273.15 K)
Advertisements
उत्तर
Molality (m) = `"n"/"W"_("solvent"("kg"))`
For sucrose solution:
m =`(4/342)/(96/1000)= 4/342xx1000/96 = 0.122"m"`
(Δ Tf)1 = (273.15 − 271.15)K = 2K
(Δ Tf)1 = Kfm = Kf × 0.122
2= Kf × 0.122 .......(1)
For glucose solution :
m=`(5/180)/(95/1000)=5/180xx1000/95= 0.292"m"`
(Δ Tf)2 =Kf × 0.292 .......(2)
Dividing eqn. (2) by (1)
`(Delta "T"_"f")_2/2 = ("K"_"f"xx0.292)/("K"_"f"xx0.122`
`(Delta"T"_"f")_2 = 0.292/0.122xx2 = 4.79`
Tf = 273.15 − 4.79 = 268.36 K
Freezing point of glucose solution will be 268.36 K
APPEARS IN
संबंधित प्रश्न
1.0 x10-3Kg of urea when dissolved in 0.0985 Kg of a solvent, decreases freezing point of the solvent by 0.211 k. 1.6x10 Kg of another non-electrolyte solute when dissolved in 0.086 Kg of the same solvent depresses the freezing point by 0.34 K. Calculate the molar mass of the another solute. (Given molar mass of urea = 60)
Calculate the mass of ascorbic acid (Vitamin C, C6H8O6) to be dissolved in 75 g of acetic acid to lower its melting point by 1.5°C. Kf = 3.9 K kg mol−1.
Define Freezing point.
Cryoscopic constant of a liquid is ____________.
Which of the following statements is false?
40 g of glucose (Molar mass = 180) is mixed with 200 mL of water. The freezing point of solution is ______ K. (Nearest integer)
[Given : Kf = 1.86 K kg mol-1; Density of water = 1.00 g cm-3; Freezing point of water = 273.15 K]
When 25.6 g of sulphur was dissolved in 1000 g of benzene, the freezing point lowered by 0.512 K. Calculate the formula of sulphur (Sr).
(Kf for benzene = 5.12 K kg mol−1, Atomic mass of sulphur = 32 g mol−1)
Ibrahim collected 10 mL each of fresh water and ocean water. He observed that one sample labeled “P” froze at 0° C while the other “Q” at -1.3° C. Ibrahim forgot which of the two, “P” or “Q” was ocean water. Help him identify which container contains ocean water, giving rationalization for your answer.
The depression in freezing point of water observed for the same amount of acetic acid, trichloroacetic acid and trifluoroacetic acid increases in the order given above. Explain briefly.
The depression in freezing point of water observed for the same amount of acetic acid, trichloroacetic acid and trifluoroacetic acid increases in the order given above. Explain briefly.
