You have a solution of two volatile liquids, A and B (assume ideal behavior). Pure liquid A has a vapor pressure of 385.0 torr and pure liquid B has a vapor pressure of 104.0 torr at the temperature of the solution. The vapor at equilibrium above the solution has double the mole fraction of substance A as the solution does. What is the mole fraction of liquid A in the solution?

the mole fraction of A in solution is 0.32

Explanation:

Let's consider a solution of two volatile liquids A and B

Vapor pressure of A is 385.0 torr

Vapor pressure of B  is 104.0 torr

According to Dalton's Law

         ---------- Equation (1)

where are partial pressure of A and B respectively.

Using Roult's Law

 ---------- Equation (2)

where;

the total vapor pressure of the solution

= mole fraction of A and B respectively

= vapor pressures of pure species of A and B

So;

Replacing our given values for and  into equation (2) ; we have:

The sum of mole fractions is equal to 1

Hence;

  ------ Equation (3)

It is given that mole fraction of vapor is equal to twice the mole fraction of liquid .

It is known that; a partial pressure of a component in gaseous phase is equal to mole fraction times the total pressures. As such;

 ------- Equation (4)

Partial Pressure is given as follows :

Thus; from equation 4

Replacing the above value into equation (8)

192.5 = 281

192.5 - 104 =

88.5 =

= 0.32

Thus, the mole fraction of A in solution is 0.32

the answer would be c

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.