Q16 of 36 Page 1

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).

4% solution (w/w) of sucrose means 4g of sucrose in 96g water

Wsolvent = 96g, wsolute= 4g, Msolute= 342 g mol-1


Using the formula, ∆Tf = kf x m


(273.15 – 271.15) =


Kf = 16.39 K


For 5% solution (w/w) of sucrose means 5g of sucrose in 95g water


Wsolvent = 95g, wsolute= 5g, Msolute= 180 g mol-1


Using the formula, ∆Tf = kf x m


∆Tf = K


= 0.48 K


Tf = Tf0 - ∆Tf = (273.15 – 0.48) K = 272.67 K


More from this chapter

All 36 →
14

(i) What is the role of activated charcoal in gas mask?

(ii) A colloidal sol is prepared by the given method in figure. What is the charge on hydrated ferric oxide colloidal particles formed in the test tube? How is the sol represented?



(iii) How does chemisorption vary with temperature?


 15

An element crystallizes in fcc lattice with a cell edge of 300 pm. The density of the element is 10.8 g cm-3. Calculate the number of atoms in 108 g of the element.

 17

(a) Name the method of refining which is

(i) used to obtain semiconductor of high purity,


(ii) used to obtain low boiling metal.


(b) Write chemical reactions taking place in the extraction of copper from Cu2S.


 18

Give reasons for the following:

(i) Transition elements and their compounds act as catalysts.


(ii) E° value for (Mn2+|Mn) is negative, whereas for (Cu2+|Cu) is positive.


(iii) Actinoids show irregularities in their electronic configuration.