Somak Chatterjee | March 6th, 2013 at 05:21pm
Laws to remember:
- Raoult’s law: For a solution of volatile liquids, the partial vapour pressure of each component in the solution is directly proportional to its mole fraction. p1 = x1p1°
- Dalton’s law of partial pressure: The total pressure over the solution phase in the container is the sum of the partial pressures of the components of the solution. ptotal = p1 + p2
- Henry’s law: Mole fraction of a gas in solution is proportional to the partial pressure of the gas over the solution. p = Khx
Formulae for numericals:
Mass % = (Mass of component in solution/ Total mass of the solution) * 100
Volume % = (Volume of component in solution/ Total volume of the solution) * 100
ppm =(No. of parts of the component/ Total no. of parts of all components of solution) * 100
Mole fraction = No. of moles of component/ Total no. of moles of all components
Molarity = (Moles of solute/ volume of solution in litres)
Molality = Moles of solute/ Mass of solvent in kg
Relative Lowering of vapour pressure
Elevation of boiling point
Depression of freezing point
Osmosis and Osmotic Pressure
van’t Hoff Factor
Questions which have been asked previously:
|2007 Set-1 Delhi
Q. Define osmotic pressure.
Q. An antifreeze solution is prepared from 222.6 g of ethylene glycol [C2H4(OH)2] and 200 g of water. Calculate the molality of the solution. If the density of this solution be 1.072 g mL−1, what will be the molarity of the solution?
2008 Set-2 Delhi
Q. State Raoult’s law for solutions of volatile liquids. Taking suitable examples explain the meaning of positive and negative deviations from Raoult’s law.
Q. Define the term osmotic pressure. Describe how the molecular mass of a substance can be determined by a method based on measurement of osmotic pressure?
2009 Set-1 Delhi
Q. Differentiate between molality and molarity of a solution. What is the effect of change in temperature of a solution on its molality and molarity?
Q. 100 mg of a protein is dissolved in just enough water to make 10.0 mL of solution. If this solution has an osmotic pressure of 13.3 mm Hg at 25°C, what is the molar mass of the protein?
2010 Set-3 Delhi
Q. Non-ideal solutions exhibit either positive or negative deviations from Raoult’s law. What are these deviations and why are they caused? Explain with one example for each type.
Q. A solution prepared by dissolving 1.25 g of oil of winter green (methyl salicylate) in 99.0 g of benzene has a boiling point of 80.31 °C. Determine the molar mass of this compound. (B.P. of pure benzene = 80.10 °C and Kb for benzene = 2.53 °C kg mol)
2011 Set-1 Delhi
Q. Differentiate between molarity and molality for a solution. How does a change in temperature influence their values? Calculate the freezing point of an aqueous solution containing 10.50 g of MgBr2 in 200 g of water. (Molar mass of MgBr2 = 184 g) (Kf for water = 1.86 K kg mol)
Q. Define the terms osmosis and osmotic pressure. Is the osmotic pressure of a solution a colligative property? Explain. Calculate the boiling point of a solution prepared by adding 15.00 g of NaCl to 250.0 g of water. (Kb for water = 0.512 K kg mol), Molar mass of NaCl = 58.44 g)
2012 Set-1 Delhi
Q. A 1.00 molal aqueous solution of trichloroacetic acid (CCl3COOH) is heated to its boiling point. the solution has the boiling point of 100.18 oC. Determine the van’t Hoff factor for trichloroacetic acid. (Kb for water = 0.512 kgmol-1)
All the best,