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
Calculate the amount of CaCl2 (molar mass = 111 g mol−1) which must be added to 500 g of water to lower its freezing point by 2 K, assuming CaCl2 is completely dissociated. (Kf for water = 1.86 K kg mol−1)
Calculate the freezing point of solution when 1.9 g of MgCl2 (M = 95 g mol−1) was dissolved in 50 g of water, assuming MgCl2 undergoes complete ionization.
(Kf for water = 1.86 K kg mol−1)
Calculate the freezing point of a solution containing 60 g of glucose (Molar mass = 180 g mol–1) in 250 g of water. (Kf of water = 1.86 K kg mol–1)
Cryoscopic constant of a liquid is ____________.
Which of the following 0.10 m aqueous solutions will have the lowest freezing point?
Which of the following statements is false?
Of the following four aqueous solutions, total number of those solutions whose freezing points is lower than that of 0.10 M C2H5OH is ______. (Integer answer)
- 0.10 M Ba3 (PO4)2
- 0.10 M Na2 SO4
- 0.10 M KCl
- 0.10 M Li3 PO4
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]
The depression in the 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 of water observed for the same amount of acetic acid, trichloroacetic acid and trifluoroacetic acid increases in the order given above. Explain briefly.
