Question

mole fraction of a in H2O is 0.2 the molarity of a in H2O is

Answer 1

The sum of all the mole fractions for the solution = 1

 

mole fraction of A = 0.2

 

so mole fraction H2O = 1 - 0.2 = 0.8

 

 

molality = moles solute / kg solvent

 

 

molar mass H2O = 1.01 * 2 + 16.00 = 18.02 g/mol

 

mass H2O = 0.8 mol H2O x [18.02 g / mol] x [1 kg / 1000 g] = 0.014 kg H2O

 

 

so molality = 0.2 / 0.014 = 14 M(approx