Question

Benzene and toluene form nearly ideal solution. At a certain temparature, calculate the vapour pressure of the solution containing equal moles of two substances.

[Given: pure partial pressure of benzene=150 mm of Hg, pure partial pressure of toluene=55 mm of Hg]

Answer 1

Final Answer: 102.5 mm Hg

Steps:
1) 
We have,
 
[tex] P^{o} _{Benzene} = 150\: mm \:Hg \\ P^{o} _{Toluene} = 75\: mm \:Hg \\ [/tex]

2) And , Both components are of equal moles;
So, Mole Fraction 
$x_{Benzene} = x_{Toluene} =0.5$

3)
    Since ,Benzene and Toluene are non-reacting gases .
By Daltons Law of Partial Pressure:
In a mixture of non recting gases ,the totalpressure exerted is equal to the sum of the partial pressure of Individual gases .

 [tex] P_{Total} = P^{o}_{Benzene} x_{Benzene} + P^{o}_{Toluene} x_{Toluene} \\ P_{Total} = 170 \times 0.5 \:\: + 55\times 0.5 \\ \\ \:\:\:\:\:\: = 102.5mmHg [/tex]


Hence ,Total Pressure exerted by vapours of given components is 102.5 mm Hg .   

Answer 2

Answer: 112.5

The solution is given in the pic