Relative lowering of vapour pressure
properties are termed as colligative properties derived from a Latin word with co meaning together ligare meaning to bind .
Relative lowering of vapour pressure
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Vapour pressure of a solvent present in solution is less than the vapour pressure of the pure solvent .
According to Raoult lowering of vapour pressure of a solution depends only on the concentration of the solute particles and remains independent of their identity .
o p1 = x1 p1 0 o The reduction in the vapour pressure of solvent ( p1 ) is given as :
As x2 = 1-x1 the above equation reduces to Δp1 = x2p1 0 o
Lowering of the vapour pressure of a solution with several nonvolatile solutes depends upon the sum of the mole fraction of different solutes which makes the above equation as-
Where n1 and n2 are the number of moles of solvent and solute respectively present in the solution .
o The above equation can be written as :