Question

(a) Number of moles of the solute per kilogram of the solvent is  

(a) Mole fraction 

(b) Molality 

(c) Molarity 

(d) Molar mass

(b) The extent to which a solute is dissociated or associated can be expressed by Van’t Ho factor.’ Substantiate the statement. 

(c) The vapour pressure of pure benzene at a certain temperature is0.850 bar. Anon volatile, non-electrolyte solid weighing 0.5 g when added to 39 g of benzene (molar mass 78 g mol^-1 ), the vapour pressure becomes 0.845 bar. What is the molar mass of the solid substance?

Answer 1

(a) (b) Molality

(b) (b) The van’t Holf factor,

When i = 1 ⇒ there is no association or dissociation of solute particles.
When i < 1 ⇒ there is association of solute particles. When i > 1 ⇒ there is dissociation of solute particles.