>>
Study Material >>
IIT JEE Chemistry >>
Physical Chemistry >>
Solutions >>
Relationship-Molality and Molarity
Relationship between molality and molarity:
Molarity/Molality = moles of solute/volume of solution × mass of solvent/moles of solute
= mass of solvent (in kg)/volume of solution (in litre) = mass of solvent (in grams)/volume of solution = W/V
Let the density of the solution be d g mL−1
Mass of solution = V × d
Mass of solute = number of moles × molecular mass of solute
= n mA
Mass of solvent, W = mass of solution – mass of solute
= V × d – n × mA
Thus, Molaity/Molality (M/m) = V×d–n×mA/V
Molaity (m) = molarity×V/V×d–n×mA
= molaity/d–n/V×mA
m = molaity/d–molaity×mA
where wZ, wB are masses of solvent and solute respectively xA and xB are mole fractions of solvent and solute respectively mA is molecular mass of solvent.