Answer to Question #221874 in Inorganic Chemistry for Huds

Question

The density of 3 mol of Nacl is 1.25 gl-1, calculate molarity of a solution

Answer 1

3 Molar solution means there are 3 moles of NaCl salt in 1 Liter. Molecular weight of NaCl = 58.44.   

Hence, there are 3×58.44 gms in 1 Litre of water.

Density =volume/mass​

Mass of 1 litre of solution = 1.25 gms/ml * 1000 ml = 1, 250 gms

V = volume of water added to make the solution

 175.32 gms + 1 gm /ml * V = 1, 250 gm

    ⟹V=1,074.68ml

So 1,074.68 ml or 1, 074.68 gms of water is mixed with 3 moles of Na Cl to make the 3 M solution.  

    

  Molality = mass of solute in number of moles / mass of solvent in kg

  =3/1.07468

​

        =2.7915 kg/mol