Advertisements
Advertisements
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)
Advertisements
उत्तर
Given:
Molar mass of CaCl2 (MB) = 111 g/mol
Weight of water (wA) = 500 g
Kf for water = 1.86 K kg/mol
ΔTf = 2 K
Formula,
`DeltaT_f=ixx(K_fxxw_Bxx1000)/(w_AxxM_B)`
CaCl2 is an electrolyte which dissociates as,
CaCl2 → Ca2+ + 2Cl
Hence, i for CaCl2 = 3
Solution:
`DeltaT_f=ixx(K_fxxw_Bxx1000)/(w_AxxM_B)`
`2 =3xx(1.86xxw_Bxx1000)/(500xx111)`
`w_B=(2xx500xx111)/(3xx1.86xx1000)`
`w_B=19.9 g`
Amount of CaCl2 required = 19.9 g
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)
Which of the following solutions shows maximum depression in freezing point?
(A) 0.5 M Li2SQ4
(B) 1 M NaCl
(C) 0.5 M A12(SO4)3
(D) 0.5 MBaC12
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)
The freezing point of equimolal aqueous solution will be highest for ____________.
Which observation(s) reflect(s) colligative properties?
(i) A 0.5 m NaBr solution has a higher vapour pressure than a 0.5 m BaCl2 solution at the same temperature.
(ii) Pure water freezes at a higher temperature than pure methanol.
(iii) A 0.1 m NaOH solution freezes at a lower temperature than pure water.
Assertion: When NaCl is added to water a depression in freezing point is observed.
Reason: The lowering of vapour pressure of a solution causes depression in the freezing point.
1.2 mL of acetic acid is dissolved in water to make 2.0 L of solution. The depression in freezing point observed for this strength of acid is 0.0198° C. The percentage of dissociation of the acid is ______. [Nearest integer]
[Given: Density of acetic acid is 1.02 g mL–1, Molar mass of acetic acid is 60 g/mol.]
Kf(H2O) = 1.85 K kg mol–1
Out of the following 1.0 M aqueous solution, which one will show the largest freezing point depression?
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 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.
