In a solvent S , a compound B is partially dissociated into C and D as given below: B 2 C + 2 D B , C and D are non-volatile in nature. The molar mass of B is 10 times the molar mass of S . The standard boiling point and the standard enthalpy of vaporization of S are 400 K and 10R J mol ⁻¹ , respectively ( R is the gas constant in J K ⁻¹ mol ⁻¹ ). A solution of B in S with an initial concentration of B as 0.25 % (mas

Step-by-step solution

The elevation in boiling point is given by T_b = i K_b m . The ebullioscopic constant K_b is calculated as: K_b = R (T_b^ )^2 M_S 1000 H_ vap Substituting the given values ( T_b^ = 400 K, H_ vap = 10R J mol ⁻¹ ): K_b = R (400)^2 M_S 1000 (10R) = 16 M_S For a dilute solution with 0.25 % (mass/mass) concentration, the mass of solute w_B = 0.25 g and the mass of solvent w_S 100 g. The molality m is: m = w_B 1000 M_B w_S = 0.25 1000 10 M_S 100 = 0.25 M_S Given T_b = 408 - 400 = 8 K, we substitute into the boiling point