If the density of a 5 M solution of KCl is 1.26 ~g ~mL ⁻¹ , then find the molality of the solution. (molecular mass of KCl =74.55 ~g ~mol ⁻¹ )

Step-by-step solution

5 molar solution means there are 5 moles of KCl salt in 1 ~L . Molecular weight of KCl =74.55 ~g ~mol ⁻¹ Hence, there are 5 74.55 ~g in 1 ~L of water Density = mass volume Mass of 1 ~L of solution =1.26 ~g / mL 1000 ~mL =1260 ~g Mass of water in solution = Mass of solution - Mass of solute =1260-372.75=887.25 ~g Mass of water in solution =0.887 ~kg Molality = Number of moles of solute Mass of solvent in kg = 5 0.887 Molality =3.38 ~m Hence, molality of the solution is 3.38 ~m .