Why is an increase in temperature observed on mixing chloroform with acetone?

Answer:

When chloroform is added to acetone there are new forces of attraction due to hydrogen bonding between acetone and chloroform.
ΔHmix is negtive because energy is released due to increase in the attractive forces, therefore dissolution is the exothermic process . hence temperature is increases.


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Why is the osmotic pressure measurement preferred for determining molecular mass of proteins?


Proteins are high molecular mass materials. The magnitude of a colligative property depends inversely on the molecular mass. For high molecular mass proteins the only colligative property which has a measurable magnitude is the osmotic pressure.
Therefore, to determine the molecular mass of proteins, osmotic pressure is preferred.
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A deci-molar solution of K4 [Fe(CN)6] is 50% dissociated at 300 K. Calculate the osmotic pressure of solution (R = 0.082)/L atm K–1)?

Answer:
The given complex is ionsiable and it dissociates as follow

K4    [ Fe (CN)6]  4K+ + [Fe(CN)6]4- 
(1-a) 4a    a 
 
Where a is the degree of dissociation of a complex.
intial moles of complex =1
moles after dissociation of the complex = 1-a + 4a+a = 1+4a

since osmotic pressure is directly proportional to the number of moles, hence
 
Pobserve/ Pnormal= (1+4a)/1

Dissociation takes place only 50% a= 0.50
P/2.462 = 1+(4 x 0.50)
p/2.462 = 1+2
p/2.462=3
p= 2.462x 3
p=7.386 atm 
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Why is osmotic pressure considered a colligative property?

Answer:

colligative property
depend on the number of solute particles irrespective of their nature relative to the total number of particles present in the solution.
Osmotic pressure depends upon the number of particles of solute, i.e., molarity of solute. Therefore, it is considered as colligative property.
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Why does the boiling point of a solvent increase by the presence of a solute in it?

Answer:

A liquid boils when its vapour pressure is equal to the atmospheric pressure. When a nonvolatile solute is added to a solvent, its vapour pressure gets lowered. Therefore, higher temperature will be required to attain the same vapour pressure. Therefore, the solution of a nonvolatile solute will boil at higher temperature than the solvent.
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