Which of the following pair of solution (aq.) contain isotonic solution at same temperature? (Assume 100 % ionisation of electrolytes) (1) 0.1 M NaCI and 0.2 M CaCI2(2) 0.1 M NaCI and 0.3 M AICI3 (3) 0.3 M NaCI and 0.1 M AICI3 (4) 0.3 M NaCI and 0.2 CaCI2

Freezing point of pure liquid A is T K. If some amount of non-electrolyte non-volatile impurity is added in A, an ideal solution is formed. On cooling at 200 K, only 30% (by mass) liquid A is present and at 201 K, 60 % (by mass) liquid A is present. The value of T is .

Liquid A and B form ideal solution at temperature T. Mole fraction of A in liquid and vapour phase are 0.4 and 4/13 respectively, when total pressure is 130 torr. The vapour pressure (in torr) of A and B in pure state at temperature T are respectively.

We know that partial pressure of components of a binary solution containing A and B component.

(1) In liquid state:

P_A= P°_A X_A and  P_B= P°_B X_B

(2) In Vapour phase: 

P_A= P_T Y_A  and P_B= P_T Y_B

Where X_A and X_B is mole fraction in liquid state while Y_A and Y_B is mole fraction in vapour phase

What is the relation between Raoult' law and Dalton's ?

According to Raoult's Law: The partial pressure of any volatile component of a solution at any temperature is equal to the vapour pressure of the pure component multiplied by the mole fraction of that component in the solution.

      Where X_A­ and X_B is the mole fraction of the component A and B in liquid phase respectively

According to Dalton's Law:

The vapour behaves like an ideal gas, then according to Dalton's law of partial pressures, the total pressure P_Tis given by:

 Partial pressure of the gas = Total pressure x Mole fraction

                                        P_A = P_T Y_A and P_B =P_T Y_B

Where Y_A­ and Y_B is the mole fraction of the component A and B in gas phase respectively

Combination of Raoult's and Dalton's Law:

(3) Thus, in case of ideal solution the vapour phase is phase is richer with more volatile component i.e., the one having relatively greater vapour pressure

Graph Between 1/Y_A Vs 1/X_A:

According to Dalton's law of partial pressures, the total pressure P_T is given by:

 Partial pressure of the gas = Total pressure x Mole fraction

Where Y_A­ and Y_B is the mole fraction of the component A and B in gas phase respectively

According to Raoult's law:

On rearrangement of this equation we get a straight line equation:

Illustrative Examples:

Liquid A and B form ideal solution at temperature T. Mole fraction of A in liquid and vapour phase are 0.4 and 4/13 respectively, when total pressure is 130 torr. The vapour pressure (in torr) of A and B in pure state at temperature T are respectively.

Solubility of gases and Henry's Law:

Sodium metal crystallizes In body centered cubic lattice with the cell edge, a= 4.29 A.What is the radius of sodium atom? (III-.JEE 1994)