. Differentiate between molarity and molality for a solution


(a) Differentiate between molarity and molality for a solution. How does a change in temperature influence their values?

(b) 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–1)

OR

(a) Define the terms osmosis and osmotic pressure. Is the osmotic pressure of a solution a colligative property? Explain

(b) Calculate the boiling point of a solution prepared by adding 15.00 g of NaCl to 250.00 g of water.

     (Kb for water = 0.512 kg mol–1),

     (Molar mass of NaCl = 58.44 g)

Best Answer

(a) Molarity is the number of moles of solute dissolved in one litre of solution whereas molality is the number of moles of solute per kilogram of the solvent. Molarity decreases with increase in temperature as volume increases with increase in temperature. Molality is independent of temperature because mass does not depend on temperature

freezing point of an aqueous solution

(a) Osmosis: The spontaneous movement of the solvent molecules either from the pure solvent to the solution or from a less concentrated solution to a more concentrated solution through a semi-permeable membrane.

Osmotic Pressure: The minimum excess pressure that has to be applied on the solution to prevent the passage of solvent molecules into it through semipermeable membrane is called osmotic pressure. Osmotic pressure is a colligative property as it depends on the number of moles of solute particles and not on their identity

osmotic

water

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