Components a and b form ideal solution. at 350 k, a liquid mixture containing 40% (mole) a is in equilibrium with a vapour containing 70% (mole) a. if the vapour pressure of a at 350 k is 70 kpa, what is the vapour pressure of b? (b) 20 kpa (d) 12 kpa (а) 25 kpa (c) 40 kpa

Answer : The correct option is, (b) 20 kPa

Explanation :

The Raoult's law for liquid phase is:

    .............(1)

where,

= partial vapor pressure of A

= vapor pressure of pure substance A

= mole fraction of A

The Raoult's law for vapor phase is:

     .............(2)

where,

= partial vapor pressure of A

= total pressure of the mixture

= mole fraction of A

Now comparing equation 1 and 2, we get:

   ............(3)

First we have to calculate the total pressure of the mixture.

Given:

and

and

Now put all the given values in equation 3, we get:

Now we have to calculate the vapor pressure of B.

Formula used :

Now put all the given values in this formula, we get:

Therefore, the vapor pressure of B is 20 kPa.

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

solute : a solute is a substance that is dissolved in another substance is known as a solvent. it is mixed with a special mixture know as homogeneous mixture.

solvent: a solvent is a substance that dissolved a solute, which results in a solution is known as solvent.