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For dilute solutions n2 << n1, hence ignoring n2 in the denominator we get
w1 and M1 = Masses and molar masses of solvent.
w2 and M2 = Masses and molar masses of solute. Elevation of boiling point o o
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Increase in temperature increases the vapour pressure of a
A liquid boils at a temperature where the vapour pressure is equal to the atmospheric
Vapour pressure of the solvent decreases in the presence of nonvolatile solute.
The boiling point of a solution is always higher than that of the boiling point of the pure solvent in which the solution is prepared as.
The elevation of boiling point also depends on the number of solute molecules rather than their nature.
The increase in the boiling point = ΔTb = Tb – Tb 0. This is known as elevation of boiling point.
Tb 0 = boiling point of pure solvent
Tb 0 = boiling point of solution
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In dilute solutions the elevation of boiling point Tb is directly proportional to the molal concentration of the solute in a solution. Mathematically,
ΔTb ∝ m ΔTb = kb m m = Molality = number of moles of solute dissolved in 1 kg of solvent
Kb = constant of proportionality. It is also known as Boiling Point Elevation Constant or Molal Elevation Constant( Ebullioscopy Constant). The unit of Kb is K kg mol-1.