Pressure of · Part 2

versus the mole fractions x and x for a solution gives a linear plot as shown in Fig. . . These lines (I and II) pass through the points for which x and x are equal to unity. Similarly the plot (line III) of p total versus x is also linear (Fig. . ). The minimum value of p total is p and the maximum value is p , assuming that component is less volatile than component , i.e., p < p . The composition of vapour phase in equilibrium with the solution is determined by the partial pressures of the components. If y and y are the mole fractions of the Fig. . : The plot of vapour pressure and mole fraction of an ideal solution at constant temperature. The dashed lines I and II represent the partial pressure of the components. (It can be seen from the plot that p and p are directly proportional to x and x , respectively). The total vapour pressure is given by line marked III in the figure. components and respectively in the vapour phase then, using Dalton’s law of partial pressures: p = y p total ( . ) p = y p total ( . ) In general p i = y i p total ( . ) Vapour pressure of chloroform (CHCl ) and dichloromethane (CH Cl ) at K are mm Hg and mm Hg respectively. (i) Calculate the vapour pressure of the solution prepared by mixing . g of CHCl and g of CH Cl at K and, (ii) mole fractions of each component in vapour phase. (i) Molar mass of CH Cl = × + × + . × = g mol – Molar mass of CHCl = × + × + . × = . g mol - Moles of CH Cl