Assuming that the magnitude of the elevation is small, T may be replaced by T0 in the denominator and hence

According to Raoult's law, the relative lowering of the vapour pressure is equal to the mole fraction of solute; that is (pe - p)/pe = x2, or p/pe = 1 - x2. Thus, ln(p/pe) = ln(1 - x2)

For small values of x2 (that is, dilute solutions), ln(1 - x2) q -x2, and equation (2.11) becomes

0 0

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