. State the following

(a) State the following:

    (i) Henry’s law about partial pressure of a gas in a mixture.

    (ii) Raoult’s law in its general form in reference to solutions.

(b) A solution prepared by dissolving 8.95 mg of a gene fragment in 35.0 mL of water has an osmotic pressure of 0.335 torr at 25°C. Assuming the gene fragment is a non-electrolyte, determine its molar mass.


(a) Differentiate between molarity and molality in a solution. What is the effect of temperature change on molarity and molality in a solution?

(b) What would be the molar mass of a compound if 6.21g of it dissolved in 24.0 g of chloroform form a solution that has a boiling point of 68.04°C. The boiling point of pure chloroform is 61.7°C and the boiling point elevation constant, Kb for chloroform is 3.63°C/m.

Best Answer

(a) (i) Henry’s law: It states that the partial pressure of the gas in vapour phase (p) is proportional to the mole fraction of the gas (x) in the solution and is expressed as:

                               P = KH x

          Where KH is Henry’s law constant

      (ii) Raoult’s law: It states that for any solution the partial pressure of each volatile component in the solution is directly proportional to its mole fraction


(a) Molarity (M): It is defined as number of moles of solute dissolved in one litre of solution


    Unit of molarity is mol L–1 or M (molar). Molarity changes with change in temperature as volume changes with change in temperature

    Molality (m): It is defined as the number of moles of the solute dissolved in one kilogram (kg) of the solvent and is expressed as

molarity and molality

molar mass

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