Numerical Problems on Colligative Properties

 Q.1 Arginine vasopressin is a pituitary harmone. It helps to regulate the amount of water in the blood by reducing the flow of urine from the kidneys. An aqueous solution containing 21.6 mg of vasopressin in 100 mL of solution had an osmotic pressure of 3.70 mm Hg at 25°C. What is the molecular weight of the harmone? 

Q.2 The osmotic pressure of blood is 7.65 atm at 37°C. How much glucose should be used per litre for an intravenous injection that is to have the same osmotic pressure as blood. 

Q.3 At 300 K, 36 g of glucose present per litre in its solution has an osmotic pressure of 4.98 bar. If the osmotic pressure of solution is 1.52 bar at the same temperature, what would be its concentration?

Q.4 At 20°C, the osmotic pressure of urea solution is 400 mm. The solution is diluted and the temperature is raised to 35°C, when the osmotic pressure is found to be 105.3 mm. Determine extent of dilution.

Q.5 An aqueous solution of 2 per cent (wt./wt.) non-volatile solute exerts a pressure of 1.004 bar at the boiling point of the solvent. What is the molecular mass of the solute?

Q.6 The vapour pressure of water is 12.3 kPa at 300 K. Calculate vapour pressure of 1 molal solution of a solute in it.

Q.7 A solution containing 30 g of a non-volatile solute exactly in 90 g water has a vapour pressure of 2.8 kPa at 298 K. Further 18 g of water is then added to solution, the new vapour pressure becomes 2.9 kPa at 298 K. 

Calculate : (i) Molecular mass of the solute, (ii) vapour pressure of water at 298 K

Q.8 Find the molality of a solution containing a non-volatile solute if the vapour pressure is 2% below the vapour pressure of pure water. 

Q.9 What will be the boiling point of bromine when 174.5 mg of octa-atomic sulphur is added to 78 g of bromine. Kb for Br2 is 5.2 K 'kg/mol and b.pt. of Br2 is 332.15 K. 

Q.10 What is the depression in freezing point of a solution of non-electrolyte if elevation in boiling point is 0.13 K, Kb = 0.52 K kg/mol ; Kf= 1.86 Kkg/mol? 


Answer:

A.1) 1085g/mol     A.2) 54.10g     A.3) 0.061 M

A.4) 4 times   A.5) 40.97g/mol     A.6) 12.08KPa

A.7) i) 23g/mol  ii) 3.53kPa   A.8) 1.1334

A.9) 332.195K   A.10) 0.465K

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