A solution of sucross (molar mass = 342 g "mol"^(-1)) has been prepared by dissolving 68.4 g of sucrose in one kg of water. K_(f) for water is "1.86 K kg mol"^(-1) and vapour pressure of water at 298 K is 0.024 atm. If on dissolving the above amount of NaCl in 1 kg of water, the freezing point is found to be -0.344^(@)C, the percentage dissociation of NaCl in the solution is

A solution of sucross (molar mass = 342 g "mol"^(-1)) has been prepare

1.	A solution of sucross (molar mass = 342 g "mol"^(-1)) has been prepared by dissolving 68.4 g of sucrose in one kg of water. K_(f) for water is "1.86 K kg mol"^(-1) and vapour pressure of water at 298 K is 0.024 atm. If on dissolving the above amount of NaCl in 1 kg of water, the freezing point is found to be -0.344^(@)C, the percentage dissociation of NaCl in the solution is
Answer» `75%` `80%` `85%` `90%` SOLUTION :`DeltaT_(f)"(calculated)"=K_(f)xxm=1.86xx(5.85)/(58.5)=0.186^(@)` `DeltaT_(f)"(OBSERVED)"=0.344^(@)C THEREFORE i=(0.344)/(0.186)=1.85` `underset(1-ALPHA)(NaCl)rarrunderset(alpha)(Na^(+))+underset(alpha)(Cl)` `=1+alpha or alpha=i-1=0.85=85%`