The correct relationship between molarity (M) and molality (m) is (d = density of the solution, in Kg L-1, M2 = molar mass of the solute in kg mol-1)

Given  M=Molarity of solution    ;     m=molality of solution        M2=MW of solute in kg     ;      d= density of solution in kg/litmolality = nsolute (in magnitude)Wsolvent = 1 kgWsolute(in kg) = nsolute X MW of solute in kgwe know ,  nsolute = m ;   MW of solute in kg = M2