2.16 Heptane and octane form an ideal solution. At , the vapour pressures of the two liquid components are and respectively. What will be the vapour pressure of a mixture of of heptane and of octane?
Vapour pressure of heptane =
and vapour pressure of octane =
Firstly we will find moles of heptane and octane so that we can find vapour pressure of each.
Molar mass of heptane = 7(12) + 16(1) = 100 unit.
and molar mass of octane = 8(12) + 18(1) = 114 unit.
So moles of heptane :
and moles of octane :
Mole fraction of heptane = 0.456 and mole fraction of octane = 0.544
Now we will find the partial vapour pressure:-
(i) of heptane :-
(ii) of octane :-
So total pressure of solution =
= 47.97 + 25.46 = 73.43 KPa